Merge pull request #7511 from haskell/wip/bump-3.6-into-.3.6

.docker/validate-8.10.4.dockerfile

.docker/validate-8.8.4.dockerfile

.github/workflows/linux.yml

.github/workflows/macos.yml

.github/workflows/windows.yml

Cabal-QuickCheck/Cabal-QuickCheck.cabal

Cabal-described/Cabal-described.cabal

Cabal-tests/Cabal-tests.cabal

Cabal-tree-diff/Cabal-tree-diff.cabal

Cabal/Cabal.cabal

Cabal/Makefile

Makefile

appveyor.yml

bootstrap/linux-8.10.1.json

bootstrap/linux-8.10.1.plan.json

bootstrap/linux-8.10.4.json

bootstrap/linux-8.10.4.plan.json

bootstrap/linux-8.6.5.json

bootstrap/linux-8.6.5.plan.json

bootstrap/linux-8.8.3.plan.json