[rickeylev]

Configuring a Python patch version newer than the built-in
MINOR_MAPPING failed in the python and pip Bzlmod extensions.
Manifest files loaded via add_runtime_manifest_files omitted the
release tag from default download URLs, single_version_override did
not require sha256 and urls when introducing a new version, and
pip.parse failed to match host interpreters when toolchain and pip
version granularities differed (such as X.Y vs. X.Y.Z or versions
inferred from pyproject.toml).

Update the python extension to include the release build version in
default manifest URLs, require sha256 and urls for new
single-version overrides, and verify requested toolchains exist in
tool_versions. Update pip.parse to resolve host interpreters across
exact, full, and major.minor version names and key index URL settings
by the resolved Python version.

Fixes #4358

[rickeylev]

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