Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

* CI: don't allow-newer for GHC 9.10

* allow-newer base for rere

* buildinfo-reference-generator: bump base bound

* cabal-testsuite: bump base bound

* CI: add GHC 9.10

* GHC 9.10 compat in testsuite: CPP symbols don't get passed to CC as
eagearly

Discussion: https://github.com/haskell/cabal/pull/9914#issuecomment-2077439625

Related GHC issue: ghc/ghc#21291

* GHC 9.10 compat in tests: disable tests regressing due to #9940

- Rename cabal.bootstrap.project
- Rename cabal.meta.project
- Rename cabal.validate-libonly.project
- Rename cabal.validate.project
- Rename cabal.release.project

This commit introduces a new build-type, Hooks. A package using this
build type should provide a SetupHooks.hs module which exports
a value `setupHooks :: SetupHooks`. This is intended to replace the
Custom setup type. This allows Cabal to have finer-grained information
about the build, instead of having an opaque Setup executable to invoke.

Tests include:

  - error when returning an invalid component diff in a
    per-component pre-configure hook
  - error when declaring pre-build rules whose dependency
    graph contains cycles
  - error when we cannot find a dependency of a pre-build rule
  - warning when there are pre-build rules that are declared but
    never demanded
  - correctness tests for SetupHooks, e.g. that
    pre-build rules are run in dependency order (see the
    `SetupHooksRuleOrdering` test)

Use -Wwarn=unused-packages for cabal-testsuite

Reverts a change that made `-Werror` be applied when building in tree Cabal, even when just developing.
Puts `-Werror` back in the `cabal.project.validate` validation project.

Fixes #9866

- Move constraints to project-cabal/constraints.config
- Remove duplicate package groups
- Groups coverage, doctest and validate are the same as the default group
- Remove duplicate validate-libonly package group
- Both validate and validate-libonly are the same
- Move Cabal & Cabal-syntax to pkgs/cabal.config
- Add install package group
- Add benchmarks package group
- Add tests package group
- Both default and libonly groups were the same set of packages that I renamed to tests
- Put install group before tests and benchmarks
- Don't repeat packages
- Add TODO and REVIEW comments on allow-newer exceptions
- Move latest.ghc configuration
- Put program-options first & separate imports
- Remove optional-packages
- Don't reiterate default value for tests and benchmarks
- Don't reiterate default value for optimization
- Add ghc-options.config
- Rename to ghc-latest.config
- Use -Werror in ghc-options.config
- Don't include ghc-options.config for doctest project
- Add project-config/pkgs.config
- Add project-config/pkgs.config importing all package groups
- Move Cabal-described to the cabal package group
- Remove cabal.project.buildinfo
- Have cabal.project.doctest import cabal.project
- Split integration tests into their own package group.
- Add back trailing newlines at EOF in projects
- Integration-tests.config needed for libonly
- Add a README for projects.