feat(dolt): add dolt database service support

[cofin]

Description

This PR adds first-class support for Dolt, a MySQL-compatible database with Git-like versioning.

Key Changes

• Clientless Core: Implemented src/pytest_databases/docker/dolt.py with 'oneshot' health checks via docker exec. No new Python client dependencies added to src/.
• Xdist Support: Fully supports database and server isolation levels for parallel test execution.
• Fixtures: Added dolt_service and xdist_dolt_isolation_level fixtures.
• Testing: Comprehensive tests in tests/test_dolt.py verifying service availability and isolation.
• Documentation: Added docs/supported-databases/dolt.rst and updated the index.
• Metadata: Updated pyproject.toml keywords.

Verification

Ran uv run pytest tests/test_dolt.py tests/test_mysql.py tests/test_mariadb.py with all tests passing (16 passed).

[provinzkraut]

This PR seems to include rustf support and changes to other DBs as well. I'm assuming this wasn't intentional?