fix reducing arity or chaperoning keyword-valued `prop:procedure`

Fix various problems, including a bad result from `procedure-arity`
and problems with chaperones and arity error messages when a
structure's `prop:procedure` value is a keyword-accepting procedure.

Merge to v6.0
fix spelling error
Better error msg for annotations on unbound ids

Closes PR 14246

Please merge to v6.0
Quote the identifier in the declaration error msg

Please merge to v6.0
separate out the error location tests

also, Rackety
improve source locations for uses of contracted variables
fix some bugs in the traversal function in any-wrap that I introduced

Also, rename the function so that errors like this don't take me as long to find
test case illustrating set! problem

(derived from drdr failure for
 scribblings/guide/contracts-examples/1-test.rkt)
improve the first-order checking for the current class/c implementation

(not strictly necessary, but the new, still pending class/c first-order
checking checks the arities of the methods and those additional
tests got put into the test suite, so the easiest thing for now
is just to make the current class/c implementation do that check too)
fix class/c first-order check for interface contracts
rackety
tiny doc typo
another fix to the first-order check I added earlier today

(discovered by the test suites run by drdr)
Fix PR14247

Add "Connection: close" to requests that we know will end after one
request.

Read upto 1K bytes at a time on requests rather than just 1 at a time.

Change closing semantics to be "close" and not "abandon"
Make syntax class for syntax properties.
Make better interface for properties with only booleans.
Minor cleanup in prims.
Cleanup duplication in check-subforms-unit.
implement a little bit of the random generation for the new ->

(just enough to pass the test suite)
fix `for-label` import of a submodule

Closes PR 14155

Merge to v6.0