* Added method for adding migrations for convering unique to primary key.
Based on existing migration for `file` table (in `db_file_storage.go`) migrations.
* Added better default migration names. Added ability to override migration name.
* Use ConvertUniqueKeyToPrimaryKey for cloud_migration_snapshot_partition table.
* Convert resource_version UQE to PK.
* Convert secret_encrypted_value UQE to PK.
* Removed extra test.
* Removed testdata.
* Remove support for renaming migrations for now. We can bring it in later, when we want to convert existing migrations for file, file_meta and setting tables.
* Revert removal of ColumnName to ease backporting, since this field is referenced from enterprise code.
* Use quoted identifiers in Postgres statement.
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