fix: support both TypeAliasType implementations

[abhinavkr26104]

Summary

• type the runtime alias-class tuple with the common type[object] base
• retain the existing TypeIs narrowing contract
• cover aliases created by both typing_extensions and Python 3.12's stdlib typing

Why

On Python 3.12, typing.TypeAliasType and typing_extensions.TypeAliasType are distinct class objects. Appending the stdlib class to a tuple inferred as containing only the backport class made the repository's strict mypy check fail.

Fixes #178

Testing

• python -m pytest tests/test_utils/test_typing.py -q (7 passed)
• python -m mypy . (success, 111 files)
• python -m pyright src/browserbase/_utils/_typing.py tests/test_utils/test_typing.py
• python -m ruff check src/browserbase/_utils/_typing.py tests/test_utils/test_typing.py
• full suite: 1219 passed, 8 skipped; 4 pre-existing Windows/environment failures tracked in Make the test suite deterministic on Windows and proxied environments #181
• full suite excluding only the four Make the test suite deterministic on Windows and proxied environments #181 cases: 1219 passed, 8 skipped