Test enable groups as specified by PR labels (#2357)

* Allow CIBW_ENABLE to control the wheels built in testing

* Set CIBW_ENABLE using PR labels

* Add docs

* Build everything on the main branch

* Add CIBW_ENABLE=all option

This was mostly for use in the `main` building case, because otherwise it's maybe a bit too easy to forget to update this file when adding an enable group

* Remove dead code

* Make unit tests robust to the value of CIBW_ENABLE

* Fix tests that explicitly choose pypy

* Fix test expectation

* Don't expect impossible wheels in expected_wheels

* Simplify logic in expected_wheels

* CircleCI- run with CIBW_ENABLE=all only on the main branch

* Azure pipelines - run with CIBW_ENABLE=all on main branch

* Update gitlab to run CIBW_ENABLE=all on main

* Set CIBW_ENABLE=all on travis - it only runs on main anyway

* Fix job name error on CircleCI

* Fix tests for graalpy

* Update the test configuration to use the label

* Remove duplication of default value. Make it affect sample build too

* Move the action to after deps are installed

* GraalPy workaround for this assumption

* Make unit test resilient to changing CIBW_ENABLE

unit_test/option_prepare_test.py

@@ -51,6 +51,7 @@ def mock_build_container(monkeypatch):
 @pytest.mark.usefixtures("mock_build_container", "fake_package_dir")
 def test_build_default_launches(monkeypatch):
     monkeypatch.setattr(sys, "argv", [*sys.argv, "--platform=linux"])
+    monkeypatch.delenv("CIBW_ENABLE", raising=False)
 
     main()