feat(manager): add inline script metadata (PEP 723) support

[mkniewallner]

Changes

Add support for Python inline script metadata, also known as PEP 723.

Context

Closes #27889.

Both the regex and the transformation from commented out TOML to actual TOML have been adapted from the Python reference version. Per the recommendation in the linked discussion, since virtually any Python file can contain such metadata, to avoid slowing down Renovate, fileMatch defaults to an empty array.

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

Just a note that I initially wanted to add a section similar to pip-compile to mention that we have an empty fileMatch by default, but I then realised there already is code in place to generate a default section for this case, as can be seen here.

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

Changes tested in https://github.com/mkniewallner/renovate-pep723, where:

• Dependency dashboard is able to parse both requests and rich dependencies
• Update dependency requests to v2.32.3 mkniewallner/renovate-pep723#2 bumping requests in the 2 files were it is present was created