Add SQLBulkLoadOperator to Common SQL Provider

[SameerMesiah97]

Description

This change introduces a new operator, SQLBulkLoadOperator, to bulk load tab-delimited files into SQL database tables.

The operator delegates to the underlying hook's bulk_load implementation, allowing each SQL provider to use its native bulk loading mechanism through a common interface. It also supports optional preoperator and postoperator SQL statements to perform common setup and cleanup tasks as part of the bulk load workflow.

Rationale

DbApiHook already exposes a common bulk_load API, which is implemented by multiple SQL providers. However, unlike run() and insert_rows(), there is currently no corresponding operator that exposes this functionality to DAG authors.

While the operator provides a convenient wrapper around the existing hook API, it also simplifies common bulk loading workflows by allowing setup and cleanup SQL to be executed as part of the same task. This avoids requiring users to implement custom PythonOperators solely to orchestrate bulk loading operations.

Tests

Added unit tests verifying that:

• SQLBulkLoadOperator correctly delegates to the underlying hook's bulk_load method.
• Optional preoperator and postoperator SQL statements are executed before and after the bulk load operation, respectively.
• Template fields are correctly rendered before invoking the underlying hook.

Example DAG

Added a new example DAG, example_sql_bulk_load, demonstrating how to bulk load a tab-delimited file into a SQL table using SQLBulkLoadOperator. The example also shows how to use preoperator and postoperator to prepare and clean up the destination table as part of the bulk load workflow.

Documentation

Added documentation for SQLBulkLoadOperator, including its supported parameters and a usage example.

Backwards Compatibility

This is a new operator and does not modify existing functionality. No breaking changes are introduced.

[SameerMesiah97]

Requesting review for this.

[shahar1]

Looks good overall!
Few minor/nit comments to address before merging.