pkg/lib: clean up names and package-scope parameter

More consistent exported names and parameters that better match the
three scope choices (installation, user, or shared) --- cleaning up
after myself.

original commit: 267ac03279

collects/compiler/commands/test.rkt

@@ -108,14 +108,11 @@
        [l
         (for-each do-test l)])]
     [packages?
-     (unless
-         (for*/or ([civs (in-list '(#t #f))]
-                   [cisw (in-list '(#f #t))])
+     (unless (for*/or ([scope (in-list '(installation user shared))])
                (define pd
-             (parameterize ([current-install-version-specific? civs]
-                            [current-install-system-wide? cisw])
+                 (parameterize ([current-pkg-scope scope])
                    (with-handlers ([exn:fail? (λ (x) #f)])
-                 (package-directory e))))
+                     (pkg-directory e))))
                (and pd (do-test pd)))
        (error 'test "Package ~e is not installed" e))]
     [else