feat: declare CATALOG_V2_CONFIGS for catalogs.yml v2 support

[aahel]

Summary

Adds UnityDatabricksConfig and HiveMetastoreDatabricksConfig schema dataclasses and declares them on DatabricksAdapter.CATALOG_V2_CONFIGS to support catalogs.yml v2 parse-time validation for Databricks catalog types.

What changed

New file: dbt/adapters/databricks/catalogs/_v2.py

• UnityDatabricksConfig — validates the config.databricks block for type: unity. Enforces file_format='parquet' when use_uniform is false/unset, 'delta' when use_uniform=true.
• HiveMetastoreDatabricksConfig — validates config.databricks for type: hive_metastore. Accepts delta, parquet, or hudi.

dbt/adapters/databricks/impl.py

CATALOG_V2_CONFIGS = {
    "unity": UnityDatabricksConfig,
    "hive_metastore": HiveMetastoreDatabricksConfig,
}

Tests

15 unit tests covering registration, valid inputs, use_uniform/file_format cross-field constraint, and invalid inputs.