Create the "racket-extra-test" to reduce dependencies.

It initially contains the two tests that use redex-driven random
testing.
Run the non-default configs tests only with gcc.
added register-finalizer-and-custodian-shutdown
db: make sqlite connections managed by custodians
fix `syntax-disarm` with a `#f` second argument
make: add job options to final `raco setup`

Closes PR 14876
fix `PLT_DELAY_FROM_ZO`

Fetching bytecode from a previously read file was broken in the case
of a bytecode file with submodules.

Closes PR 14878
raco pkg docs: index fields for package-level "info.rkt"
net/http-client: add a `#:method` argument to `http-conn-recv!`

Supplying a 'HEAD method is necessary to receive the response
to a 'HEAD request, since the response will not include data.
Improve formatting in `raco pkg show`, and add single-package show.

* `raco pkg show typed-racket` now shows just the "typed-racket" pkg.

* `raco pkg show --rx typed-racket` shows all packages that match the
  regular expression "typed-racket".

* `raco pkg show` now only shows the first 8 characters of checksums
  unless you provide the `--full-checksum` argument.
add cons/dc
make: fix bootstrap for native libraries

Restore (but in a hopefully better way) a step that installs native
libraries before trying a full `raco setup`, since the libraries
may be needed for the setup proces --- especially on Windows.
make: fix for PKGS=""
raco setup: try harder to delete files such as DLLs

If "sqlite3.dll" is installed as a foreign library but shouldn't
be, then `raco setup` cannot simply deleet the file, because
starting `raco setup` opened the DLL. To avoid that problem,
rename the file to start with "raco-setup-delete-", then attempt to
delete the renamed file; the delete won't work, but the file
will be moved out of the way, and a future `raco setup` can
clean up.

The prefix "raco-setup-delete-" thus becomes special on Windows for
the directories that hold foreign libraries, shared files, and
man pages, because `raco setup` will try to delete any file
that starts with "raco-setup-delete-".

It's all very ugly, but I don't have a better idea for the
problems that I keep hitting.
improve the way '() is treated as a constant
so it fits in with stronger and whatnot and
the other list contracts
fix buggy test case
fix #:list-contract? argument
raco pkg update: fix reoprting for `--all` in a scope without packages
raco pkg: fix tests for change `raco pkg show` output
raco pkg update: change printout to avoid alarming "Removing..."

Changed "Removing" to "Uninstalling to prepare re-install of".