Move tests to rules_haskell_test module

[ylecornec]

To prepare for bzlmod support, this PR moves most tests from rules_haskell to a dedicated module called rules_haskell_tests.

Testing rules_haskell from another module is more realistic (which is particularly important with bzlmod since different modules have different visibility and repository mappings). In addition, once bzlmod is activated, the rules_haskell_test module will be able to depend on the rules_haskell_nix module which will be used to register the the nix toolchains (to avoid a dependency between rules_haskell and rules_nixpkgs).

Some comments

• Some targets are still present in rules_haskell's test folder for tests that do not test the public api but are internal to the module such as the shellcheck ones or //tests/package_configuration:package_configuration_test.

• Dependencies from the WORKSPACE and the non_module_deps_* files are split between the two modules. And the dependencies from non_module_dev_dep_* files will be development dependencies with bzlmod.

About the CI

• The CI was updated so that tests for rules_haskell and rules_haskell_tests happen in parallel. So there are more jobs but the tests for the rules_haskell module should be quick since most tests are now in rules_haskell_tests.

• The config was also updated so that rules_haskell and rules_haskell_test use separate caches on windows. This works around undeclared inclusions issues such as this one.
  This can happen because the *.d files (that keep track of C dependencies for hermeticity purposes) such as the one file from this cache hit contain absolute paths that are not the same for both module and should not be shared.

• The mergify configuration was updated but I think this is not effective until the PR is merged, so it will have to be merged manually.

[avdv]

Thank you, LGTM!

Could you please adjust the README to include a few words on how to run tests now?

BTW, for rules_sh we added the test module (as a local repository) to the root WORKSPACE too, so you could run all tests with bazel test //... @rules_sh_tests//.... Maybe this could be done here too, making it a bit easier to run the tests? What do you think?

[aherrmann]

BTW, for rules_sh we added the test module (as a local repository) to the root WORKSPACE too, so you could run all tests with bazel test //... @rules_sh_tests//.... Maybe this could be done here too, making it a bit easier to run the tests? What do you think?

I would not spend much effort in that direction. WORKSPACE are not loaded transitively, so testing bazel test @rules_sh_test//... is quite different from cd test && bazel test .... It's also not applicable to the bzlmod world since library modules are not allowed to use local overrides.