This seems to have been broken for almost a year.

- Add missing packages to cabal.project
- Allow newer `numerals` deps, as in Stack (this was mentioned in
  #5142 (comment)
  but never made it in)
- Disable `terminfo` flag for haskeline, as in Stack (eliminates a
  complaint about not finding libtinfo.so)
- Add a constraint on text-builder, since 1.0.0 has been released, but
  is incompatible

This also adds some comments and sorts the constraints list.

This reduces the chance of not setting flags on individual packages (for
example., I added unison-runtime in the previous commit, but didn’t set
these flags, and it resulted in a bunch of warnings)

It also adds flags that were missing relative to stack.yaml, and it’s
lenient with deprecations in the Cabal build, as described in the
comment there.

This should make our builds more consistent between Stack & Cabal.

Makes it easier to keep cabal.project up to date if you can eyeball things.

The one substantive change here is that cabal.project adds `constraints`
for non-Stackage packages that are pinned in stack.yaml.

It previously applied to a caching step, but now applies to the `on.pull_request.paths`.

Cabal failing to build the package won’t cause any CI jobs to fail, but
it will add a comment to the PR. The comment is removed when the Cabal
build is fixed.