Add `per-file-target-version` option (#16257)
## Summary
This PR is another step in preparing to detect syntax errors in the
parser. It introduces the new `per-file-target-version` top-level
configuration option, which holds a mapping of compiled glob patterns to
Python versions. I intend to use the
`LinterSettings::resolve_target_version` method here to pass to the
parser:
https://github.com/astral-sh/ruff/blob/f50849aeef51a381af6c27df8595ac0e1ef5a891/crates/ruff_linter/src/linter.rs#L491-L493
## Test Plan
I added two new CLI tests to show that the `per-file-target-version` is
respected in both the formatter and the linter.
