📝 Make "setuptools entrypoint" term generic

This feature grew out of `setuptools` but the modern interface for
extracting this information from the distribution package metadata
is `importlib.metadata`. So the patch attempts to reflect this in
the documentation messaging.

Refs:
* https://docs.python.org/3/library/importlib.metadata.html#entry-points
* https://packaging.python.org/en/latest/guides/creating-and-discovering-plugins/#using-package-metadata
* https://packaging.python.org/en/latest/specifications/entry-points/#entry-points

testing/test_assertion.py

@@ -223,7 +223,7 @@ class TestImportHookInstallation:
     ) -> None:
         monkeypatch.delenv("PYTEST_DISABLE_PLUGIN_AUTOLOAD", raising=False)
         # Make sure the hook is installed early enough so that plugins
-        # installed via setuptools are rewritten.
+        # installed via distribution package are rewritten.
         pytester.mkdir("hampkg")
         contents = {
             "hampkg/__init__.py": """\

testing/test_helpconfig.py

@@ -10,7 +10,7 @@ def test_version_verbose(pytester: Pytester, pytestconfig, monkeypatch) -> None:
     assert result.ret == 0
     result.stdout.fnmatch_lines([f"*pytest*{pytest.__version__}*imported from*"])
     if pytestconfig.pluginmanager.list_plugin_distinfo():
-        result.stdout.fnmatch_lines(["*setuptools registered plugins:", "*at*"])
+        result.stdout.fnmatch_lines(["*registered third-party plugins:", "*at*"])
 
 
 def test_version_less_verbose(pytester: Pytester, pytestconfig, monkeypatch) -> None: