Minor.Operation Contract Split

BREAKING CHANGE: Rename adapter operation contracts and fields.

AdapterStatement becomes DataManipulationOperation, and statement becomes operation.

Add separate adapter execution methods for DML and migration/DDL operations: execute for DataManipulationOperation requests and migrate for DataMigrationOperation requests.

Add adapter introspection methods with optional transaction context: hasTable(table, transaction?) and hasColumn(table, column, transaction?).