Rename projects to have `.project` extension (backport #9958) (#10040)

* Rename projects to cabal.*.project

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

(cherry picked from commit d8147f62)

# Conflicts:
#	.github/workflows/quick-jobs.yml
#	Makefile
#	cabal.bootstrap.project

* Fix conflict with #9990

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Co-authored-by: Phil de Joux <philderbeast@gmail.com>
Co-authored-by: brandon s allbery kf8nh <allbery.b@gmail.com>
Co-authored-by: Artem Pelenitsyn <a.pelenitsyn@gmail.com>