Enhance executemany() to use multistatement

[methane]

This pull request introduces a new executemany_fallback option to improve how executemany() handles non-bulk DML statements, allowing for client-side multi-statement batching. It also adds a new more_results() method to the connection API, enhances documentation, and expands test coverage for these features.

Enhancements to executemany() batching and options:

• Added a new executemany_fallback option to the Connection and Cursor classes, allowing users to control whether non-bulk DML statements in executemany() are executed in a loop (default) or batched into multi-statement queries ("multi"). This includes validation, documentation, and support for configuration via connection parameters. [1] [2] [3] [4] [5] [6] [7] [8]
• Implemented batching logic in Cursor.executemany() for the "multi" fallback, including statement batching, error handling, and result validation.

API improvements:

• Added a new more_results() method to the connection object, allowing users to check for additional results after a multi-statement query, and documented its usage. [1] [2] [3]

Documentation updates:

• Expanded user guide documentation to describe the new executemany_fallback option, its configuration, and the behavior of executemany() with batching. [1] [2]
• Documented the new more_results() method in the user guide and API reference.

Testing improvements:

• Added new tests for the executemany_fallback option, including validation of connection and subclass defaults, and extended multi-statement tests to cover the new API. [1] [2] [3] [4] [5] [6]

Regular expression and utility enhancements:

• Refactored and extended regular expressions and helper functions to support new batching and DML detection logic in cursors.py. [1] [2]

These changes provide more flexible and performant handling of bulk and non-bulk DML operations, better error handling, and improved developer experience through new APIs and documentation.

[codecov]

Codecov Report

❌ Patch coverage is 94.64286% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.72%. Comparing base (e2a908b) to head (4bd318b).
⚠️ Report is 52 commits behind head on main.

Files with missing lines	Patch %	Lines
src/MySQLdb/cursors.py	94.39%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #798      +/-   ##
==========================================
+ Coverage   88.86%   91.72%   +2.86%     
==========================================
  Files           7        7              
  Lines         548      665     +117     
==========================================
+ Hits          487      610     +123     
+ Misses         61       55       -6     

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