Bumps base bound, fixing #67.

See ghc#22633

and https://github.com/haskell/directory/issues/147

In cabal 3.8.1.0 --ghc-options specified on command line only passes the options to local packages. Therefore setting `EXTRA_HC_OPTS=-dcore-lint` will only pass the option to the top-level package when it's built but none of the dependencies. This at least wastes work later if we try and recompile a dependency, or worse, it might just be we never compile it with core-lint.

Instead we should modify the `cabal.project` and add a section like:

```
package *
   ghc-options: -dcore-lint
```

Fixes #66

See ghc#22623 for the assertion
failure

This commit introduces a new variable `SLOW_VALIDATE`, which when set
will try to use a compiler which is built using the `SLOW_VALIDATE`
flavour (which has assertions enabled) rather than a release compiler.

Fixes #62

This should also fix #61 which used to fail because sometimes "latest"
referred to a release pipeline and sometimes a normal validate pipeline.

The `digest` package was recently updated to use pkgconfig-depends and
it seems no other package is currently using that.

```
Failed to build digest-0.0.1.4. The failure occurred during the configure
step.
Build log (
/root/.cabal/logs/ghc-9.5.20221212/digest-0.0.1.4-6f5dd36ec9a53c3200c5420c1f28a4664af2530fcdf2e6b86a9bf9f10bcd3003.log
):
Configuring library for digest-0.0.1.4..
*** systool:cc:
systool:cc: alloc=235344 time=0.830
cabal: The program 'pkg-config' version >=0.9.0 is required but it could not
be found.
cabal: Failed to build digest-0.0.1.4 (which is required by test-futhark-1.0).
See the build log above for details.
```

This adds patches for the remaining (non-deprecated) libraries in this
list:

https://github.com/haskell/core-libraries-committee/issues/91#issuecomment-1278299233

The latest Hackage versions of these libraries now support HEAD.

Changes due to ghc@d87f28d8

The latest Hackage versions now compile with HEAD.

For now, we point the `build-9.4` job to the URL that it happens to be using at
the moment for release bindists. It is possible that this URL may change in the
future, however.

We move around some uses of `coerce` to avoid coercing underneath `IO`, which
triggers ghc#22519 on HEAD.

Using 'needs' broke CI:
https://gitlab.haskell.org/ghc/head.hackage/-/pipelines/57782

'dependencies' doesn't care if the dependency exists or not, but 'needs'
does.

;)

Run jobs greedily rather than relying on staging.
https://docs.gitlab.com/ee/ci/yaml/#needs

Further improves the life of head.hackage CI dungeoneers.

This expands the number of modes from two to four, allowing one to
separate running the build from running tests.

This change is backwards-compatible. No existing behavior is changed.

Fixes #57.

This includes `proto3-wire`, which now compiles on HEAD by virtue of
`word-compat-0.0.6` exporting compatibility shims for `Word64`/`W64#`.

These are required to satisfy the new quantified superclasses for
`{Eq,Ord,Read,Show}1`.

Patch taken from
https://github.com/kazu-yamamoto/unix-time/pull/59