[Python APIView] update supported py versions + related fixes

[swathipil]

fixes: #9557

Adding support for Python versions 3.9-3.14 (since only 3.10 was working) to available for use by the azpysdk CLI command for api.md generation.

TODO:

• add + test 3.14
• add test that generates SDK from tsp with all possible syntax and runs across all py versions

[Copilot]

Pull request overview

Updates the Python APIView stub generator and its test package to reflect newer supported Python versions (dropping older runtimes and adding newer ones), along with parsing/test adjustments to keep output stable across Python 3.9–3.13.

Changes:

• Bump apiview-stub-generator to 0.3.28 and update supported Python versions in packaging metadata and changelog.
• Expand CI to run tox-based tests across Python 3.9–3.13 and adjust tests/fixtures for version-specific behavior.
• Improve class/function parsing to better preserve source-level base class/keyword representations (e.g., metaclass) and normalize TypedDict/forward-ref rendering.

Reviewed changes

Copilot reviewed 17 out of 20 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/python-packages/apiview-stub-generator/tests/dataclass_parsing_test.py	Makes dataclass expectations version-aware and skips KW_ONLY test on <3.10.
packages/python-packages/apiview-stub-generator/tests/class_parsing_test.py	Updates expected TypedDict/Enum output and adds regression tests for forward-ref bases and EnumMeta naming.
packages/python-packages/apiview-stub-generator/tests/azure_tests/token_files/azure-eventhub-checkpointstoreblob_python.json	Updates stored token output metadata for parser 0.3.28.
packages/python-packages/apiview-stub-generator/tests/azure_tests/token_files/azure-eventhub-checkpointstoreblob-aio_python.json	Updates stored token output metadata for parser 0.3.28.
packages/python-packages/apiview-stub-generator/tests/apiview_test.py	Adjusts diagnostic count expectation based on Python version behavior.
packages/python-packages/apiview-stub-generator/setup.py	Updates python_requires and classifiers to newer Python versions.
packages/python-packages/apiview-stub-generator/ci.yml	Runs test suite under Python 3.9–3.13 in CI.
packages/python-packages/apiview-stub-generator/apistub/nodes/_function_node.py	Guards against non-function AST nodes from astroid.extract_node.
packages/python-packages/apiview-stub-generator/apistub/nodes/_class_node.py	Adds AST-based base/keyword extraction, TypedDict normalization, and annotation handling consistency.
packages/python-packages/apiview-stub-generator/apistub/nodes/_base_node.py	Fixes Optional wrapping detection differences in Python 3.9 string representations.
packages/python-packages/apiview-stub-generator/apistub/_version.py	Bumps version to 0.3.28.
packages/python-packages/apiview-stub-generator/CHANGELOG.md	Documents 0.3.28 changes and version support updates.
packages/python-packages/apistubgentest/setup.py	Updates supported Python classifiers and python_requires.
packages/python-packages/apistubgentest/apistubgentest/models/_models.py	Adds new model for forward-ref base testing and updates typing syntax for 3.9 compatibility.
packages/python-packages/apistubgentest/apistubgentest/models/_mixin.py	Updates typing syntax for 3.9 compatibility.
packages/python-packages/apistubgentest/apistubgentest/models/_dataclasses.py	Gates KW_ONLY usage to 3.10+ and imports accordingly.
packages/python-packages/apistubgentest/apistubgentest/models/init.py	Conditionally imports KW_ONLY dataclass and adds new exports.

Comments suppressed due to low confidence (1)

packages/python-packages/apistubgentest/apistubgentest/models/init.py:59

• __all__ includes "DataClassWithKeywordOnly" unconditionally, but on Python < 3.10 that symbol is never imported/defined (it's gated behind if sys.version_info >= (3, 10)). This will break from apistubgentest.models import * on 3.9 with an AttributeError. Consider only adding this name to __all__ when running on 3.10+, or always defining it (e.g., via a safe import/placeholder) so __all__ is accurate for each supported version.

    "DataClassSimple",
    "DataClassWithFields",
    "DataClassDynamic",
    "DataClassWithKeywordOnly",
    "DataClassWithPostInit",