fix(uv): index stub packages in Gazelle manifests

[TrapsterDK]

AI written, human reviewed.

Closes #1364.

Add opt-in stub-package indexing to gazelle_python_manifest.

When include_stub_packages = True, the manifest generator adds synthetic mappings for normalized distributions following the stub conventions supported by rules_python:

• types_*
• stubs_*
• *_types
• *_stubs

This allows the Gazelle Python extension to automatically add dependencies such as types-requests and asyncpg-stubs alongside their runtime packages.

The option defaults to False, matching the compatibility behavior introduced by bazel-contrib/rules_python#2425.

Related work:

• aspect-build/rules_py#841
• aspect-build/rules_py#778
• bazel-contrib/rules_python#2425
• bazel-contrib/rules_python#3199

Changes are visible to end-users: yes

• Searched for relevant documentation and updated as needed: yes
• Breaking change (forces users to change their own code or config): no
• Suggested release notes appear below: yes

gazelle_python_manifest now supports include_stub_packages = True, allowing Gazelle to automatically resolve conventional Python stub distributions from uv-managed dependencies.

Test plan

• New unit coverage for all supported stub-package naming conventions
• Updated the uv-Gazelle end-to-end manifest snapshot with types_requests
• bazel test //uv/private/gazelle_manifest:test
• bazel build //uv-gazelle-778:gazelle_python_manifest from the e2e/cases workspace
• Ruff
• Pyright
• ty
• Buildifier