feat: remove GraalPy 3.11 (gp311) support (#2895)

Drops the GraalPy 3.11 / GraalPy 24.2 builds (gp311_242) as agreed in
pypa/cibuildwheel#2741: a ~6-month overlap after the GraalPy 25 (gp312)
release. GraalPy 3.12 (gp312_250) stays.

This also removes the GraalPy 24-only workarounds that were explicitly
marked "Remove when GraalPy 24.x is dropped":
- the Visual Studio compiler-discovery (vswhere) and build-isolation
  (graalpython#491) workarounds in the Windows backend
- the issue-491 Windows skip/filter hacks in test_pep518 and
  test_dependency_versions (added in the original GraalPy PR #1538 and
  unneeded since GraalPy 25 per #2597)

The uv-doesn't-support-graalpy skip (#2754), the `graalpy` enable group,
and the generated constraints pins apply to all GraalPy and are kept.

Assisted-by: ClaudeCode:claude-opus-4.8

unit_test/build_selector_test.py

@@ -199,7 +199,7 @@ def test_build_limited_python() -> None:
     assert build_selector("cp37-win32")
     assert build_selector("cp38-win32")
     assert build_selector("pp37-win_amd64")
-    assert build_selector("gp311_242-win_amd64")
+    assert build_selector("gp312_250-win_amd64")
 
 
 def test_build_limited_python_partial() -> None:

unit_test/option_prepare_test.py

@@ -14,7 +14,7 @@ from cibuildwheel.oci_container import OCIPlatform
 from cibuildwheel.util import file
 
 DEFAULT_IDS = {"cp39", "cp310", "cp311", "cp312", "cp313", "cp314", "cp314t"}
-ALL_IDS = DEFAULT_IDS | {"pp39", "pp310", "pp311", "gp311_242", "gp312_250"}
+ALL_IDS = DEFAULT_IDS | {"pp39", "pp310", "pp311", "gp312_250"}
 
 
 @pytest.fixture
@@ -158,7 +158,6 @@ before-all = "true"
             "pp39",
             "pp310",
             "pp311",
-            "gp311_242",
             "gp312_250",
         }
     }
@@ -180,7 +179,6 @@ before-all = "true"
             "pp39",
             "pp310",
             "pp311",
-            "gp311_242",
             "gp312_250",
         ]
     }