Recognise uv >= 0.12.14 resolution errors

[wenceslas-sanchez]

What are you trying to accomplish?

Fixes #16510

Since uv 0.12.14, which Dependabot picked up in #16276 (0.12.7 → 0.12.15), uv reports resolution and build failures as error: / cause: instead of × / ╰─▶. The regexes in LockFileErrorHandler and PipCompileVersionResolver only matched the × form. So a conflict between two pinned packages came back as a generic DependencyFileNotResolvable carrying uv's raw output, not as UpdateNotPossible, and LockFileResolver#resolvable? raised instead of returning false.

This makes the regexes accept both prefixes, since uv 0.12.13 and earlier still print ×.

Anything you want to highlight for special attention from reviewers?

In PipCompileVersionResolver I also dropped the trailing : from the pattern, because uv >= 0.12.14 no longer prints one after "No solution found when resolving dependencies". The old × alternative still requires the leading space, as before. This also lets the old format's … for split (…): variant match, which it didn't before.

I kept the existing ×-format specs and added error:-format ones next to them, so both formats stay covered.

How will you know you've accomplished your goal?

The error:-format specs use uv 0.12.18 output (trimmed), for a pinned pair (opentelemetry-api==1.26.0 with opentelemetry-sdk==1.25.0), a conflict without a pinned pair, and a failing setup.py build. They fail on main and pass with this change. The ×-format pip-compile spec is a regression guard and passes on both. The existing uv specs still pass.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.