clean up exports of racket/contract/combinator

It used to have a (provide (except-out (all-from-out <private-file>) ...))
    and various private functions leaked to the outside over the years.

    None of the ones removed in this commit were documented, so hopefully
    they weren't being used. But this is definitely not backwards compatible,
    so this commit is mostly about testing the waters

racket/collects/racket/async-channel.rkt

@@ -245,7 +245,7 @@
 (struct base-async-channel/c (content))
 
 (struct chaperone-async-channel/c base-async-channel/c ()
-  #:property prop:custom-write custom-write-property-proc
+  #:property prop:custom-write contract-custom-write-property-proc
   #:property prop:chaperone-contract
   (build-chaperone-contract-property
    #:name async-channel/c-name
@@ -255,7 +255,7 @@
    #:projection (ho-projection chaperone-async-channel)))
 
 (struct impersonator-async-channel/c base-async-channel/c ()
-  #:property prop:custom-write custom-write-property-proc
+  #:property prop:custom-write contract-custom-write-property-proc
   #:property prop:contract
   (build-contract-property
    #:name async-channel/c-name

racket/collects/racket/contract/combinator.rkt

@@ -4,34 +4,93 @@
          "private/guts.rkt"
          "private/blame.rkt")
 
-(provide 
+(provide prop:contract
- (except-out (all-from-out "private/prop.rkt")
+         prop:flat-contract
-             contract-struct-name  
+         prop:chaperone-contract
-             contract-struct-first-order
+         
-             contract-struct-projection
+         contract-property?
-             contract-struct-val-first-projection
+         build-contract-property
-             contract-struct-stronger?
+         
-             contract-struct?
+         chaperone-contract-property?
-             chaperone-contract-struct?
+         
-             flat-contract-struct?
+         flat-contract-property?
-             make-chaperone-contract
+         
-             make-flat-contract
+         make-contract
-             build-chaperone-contract-property
+         
-             build-flat-contract-property)
+         prop:opt-chaperone-contract
- 
+         prop:opt-chaperone-contract?
- (except-out (all-from-out "private/guts.rkt")
+         prop:opt-chaperone-contract-get-test
-             check-flat-contract
+         
-             check-flat-named-contract
+         prop:orc-contract
-             make-predicate-contract
+         prop:orc-contract?
-             has-contract?
+         prop:orc-contract-get-subcontracts
-             value-contract)
+         
- 
+         prop:recursive-contract
- (except-out (all-from-out "private/blame.rkt") make-blame)
+         prop:recursive-contract?
- (rename-out [-make-chaperone-contract make-chaperone-contract]
+         prop:recursive-contract-unroll
-             [-make-flat-contract make-flat-contract]
+         
-             [-build-chaperone-contract-property build-chaperone-contract-property]
+         prop:arrow-contract 
-             [-build-flat-contract-property build-flat-contract-property])
+         prop:arrow-contract?
- skip-projection-wrapper?)
+         prop:arrow-contract-get-info
+
+         coerce-contract
+         coerce-contracts
+         coerce-flat-contract
+         coerce-flat-contracts
+         coerce-chaperone-contract
+         coerce-chaperone-contracts
+         coerce-contract/f
+         
+         build-compound-type-name
+         
+         contract-stronger?
+         list-contract?
+         
+         contract-first-order
+         contract-first-order-passes?
+         
+         prop:contracted prop:blame
+         impersonator-prop:contracted impersonator-prop:blame
+         has-blame? value-blame
+         
+         ;; helpers for adding properties that check syntax uses
+         define/final-prop
+         define/subexpression-pos-prop
+         define/subexpression-pos-prop/name
+         
+         contract-continuation-mark-key
+         
+         (struct-out wrapped-extra-arg-arrow)
+
+         blame?
+         blame-source
+         blame-positive
+         blame-negative
+         blame-contract
+         blame-value
+         blame-original?
+         blame-swapped?
+         blame-swap
+         blame-replace-negative ;; used for indy blame
+         blame-update ;; used for option contract transfers
+         blame-add-context
+         blame-add-unknown-context
+         blame-context
+         blame-add-missing-party
+         blame-missing-party?
+         raise-blame-error
+         current-blame-format
+         (struct-out exn:fail:contract:blame)
+
+         (rename-out [custom-write-property-proc contract-custom-write-property-proc])
+
+         (rename-out [-make-chaperone-contract make-chaperone-contract]
+                     [-make-flat-contract make-flat-contract]
+                     [-build-chaperone-contract-property build-chaperone-contract-property]
+                     [-build-flat-contract-property build-flat-contract-property])
+         skip-projection-wrapper?
+
+         blame-fmt->-string)
 
 (define skip-projection-wrapper? (make-parameter #f))
 
@@ -199,4 +258,3 @@
          (λ (x)
            (x-acceptor x)
            x))))
-

racket/collects/racket/private/class-c-old.rkt

@@ -947,7 +947,7 @@
    absents absent-fields 
    internal opaque? name)
   #:omit-define-syntaxes
-  #:property prop:custom-write custom-write-property-proc
+  #:property prop:custom-write contract-custom-write-property-proc
   #:property prop:contract
   (build-contract-property
    #:late-neg-projection class/c-late-neg-proj
@@ -1382,7 +1382,7 @@
                            (base-instanceof/c-class-ctc that))))
 
 (define-struct base-instanceof/c (class-ctc)
-  #:property prop:custom-write custom-write-property-proc
+  #:property prop:custom-write contract-custom-write-property-proc
   #:property prop:contract
   (build-contract-property 
    #:late-neg-projection instanceof/c-late-neg-proj
@@ -1484,7 +1484,7 @@
                (contract-stronger? this-ctc that-ctc))))))
 
 (define-struct base-object/c (methods method-contracts fields field-contracts)
-  #:property prop:custom-write custom-write-property-proc
+  #:property prop:custom-write contract-custom-write-property-proc
   #:property prop:contract
   (build-contract-property
    #:late-neg-projection instanceof/c-late-neg-proj

racket/collects/racket/stream.rkt

@@ -272,7 +272,7 @@
 (struct base-stream/c (content))
 
 (struct chaperone-stream/c base-stream/c ()
-  #:property prop:custom-write custom-write-property-proc
+  #:property prop:custom-write contract-custom-write-property-proc
   #:property prop:chaperone-contract
   (build-chaperone-contract-property
    #:name stream/c-name
@@ -281,7 +281,7 @@
    #:projection (ho-projection chaperone-stream)))
 
 (struct impersonator-stream/c base-stream/c ()
-  #:property prop:custom-write custom-write-property-proc
+  #:property prop:custom-write contract-custom-write-property-proc
   #:property prop:contract
   (build-contract-property
    #:name stream/c-name