fix(re): Export re.error and other public members

This commit adds an `__all__` list to `src/stdlib/re.py` to explicitly
define the public API of the module. This ensures that `re.error`
and other key components like `match`, `compile`, `search`, `findall`,
`sub`, `CompiledRegex`, and `MatchObject` are correctly exported and
accessible via `from stdlib.re import ...`.

This addresses the issue where `re.error` was not directly importable.

Author: google-labs-jules[bot]