gh-117089: Move importlib.metadata tests to their own package (#117092)

* Ensure importlib.metadata tests do not leak references in sys.modules.

* Move importlib.metadata tests to their own package for easier syncing with importlib_metadata.

* Update owners and makefile for new directories.

* Add blurb

Author: jaraco

.github/CODEOWNERS

@@ -119,7 +119,7 @@ Python/dynload_*.c            @ericsnowcurrently
 Lib/test/test_module/         @ericsnowcurrently
 Doc/c-api/module.rst          @ericsnowcurrently
 **/*importlib/resources/*     @jaraco @warsaw @FFY00
-**/importlib/metadata/*       @jaraco @warsaw
+**/*importlib/metadata/*       @jaraco @warsaw
 
 # Dates and times
 **/*datetime*                 @pganssle @abalkin

Lib/test/test_importlib/data/__init__.py renamed to Lib/test/test_importlib/metadata/__init__.py

@@ -9,6 +9,7 @@
 import functools
 import contextlib
 
+from test.support import import_helper
 from test.support.os_helper import FS_NONASCII
 from test.support import requires_zlib
 
@@ -85,6 +86,7 @@ def add_sys_path(dir):
     def setUp(self):
         super().setUp()
         self.fixtures.enter_context(self.add_sys_path(self.site_dir))
+        self.fixtures.enter_context(import_helper.isolated_modules())
 
 
 class SiteBuilder(SiteDir):
@@ -348,7 +350,7 @@ def DALS(str):
 
 @requires_zlib()
 class ZipFixtures:
-    root = 'test.test_importlib.data'
+    root = 'test.test_importlib.metadata.data'
 
     def _fixture_on_path(self, filename):
         pkg_file = resources.files(self.root).joinpath(filename)

Lib/test/test_importlib/_context.py renamed to Lib/test/test_importlib/metadata/_context.py

@@ -2351,10 +2351,11 @@ TESTSUBDIRS=	idlelib/idle_test \
 		test/test_import/data/unwritable \
 		test/test_importlib \
 		test/test_importlib/builtin \
-		test/test_importlib/data \
 		test/test_importlib/extension \
 		test/test_importlib/frozen \
 		test/test_importlib/import_ \
+		test/test_importlib/metadata \
+		test/test_importlib/metadata/data \
 		test/test_importlib/namespace_pkgs \
 		test/test_importlib/namespace_pkgs/both_portions \
 		test/test_importlib/namespace_pkgs/both_portions/foo \

Lib/test/test_importlib/_path.py renamed to Lib/test/test_importlib/metadata/_path.py

@@ -0,0 +1 @@
+Consolidated tests for importlib.metadata in their own ``metadata`` package.