[ty] Skip scripts with an invalid PEP 723 configuration (#27505)
## Summary
Skip checking scripts with invalid PEP 723 metadata blocks, that are,
blocks that ty can't parse successfully or configurations that don't
resolve successfully. Instead, emit one diagnostic that points to the
invalid metadata.
ty still initializes a `Program` for each of those scripts so that LSP
operations continue to work. But we skip those scripts in all code paths
where we perform semantic checks.
Fixes https://github.com/astral-sh/ty/issues/4181.
## Test plan
Added tests
