In conjunction with a small change to syntax/parse, this means
that `typed/racket/base` no longer depends on `racket/set`,
`racket/contract/base`, or `racket/generic`.
Timings on my machine go from ~200ms for `#lang typed/racket/base`
as the whole file, to ~100ms. For comparison, `racket/base` is 30ms
and `#lang racket` is 150ms. `#lang typed/racket` is ~200ms with
this change.
Changes include:
- not using `in-syntax`
- switching to `syntax/parse/pre`
- avoiding `template` from `syntax/parse`
583ca906b3