wrap before/after_cursor_execute event hooks in error handling

wrap before/after_cursor_execute event hooks in error handling

Expanded try/except error handling in _exec_single_context(),
_exec_insertmany_context(), and _cursor_execute() to encompass the
before_cursor_execute and after_cursor_execute event hooks. This
ensures that exceptions raised within these hooks, including
BaseException subclasses such as asyncio.CancelledError, are
properly handled via _handle_dbapi_exception(), providing correct
connection invalidation and pool notification.

Also added a guard in _handle_dbapi_exception to avoid
double-wrapping exceptions that are already StatementError
instances, which could occur when _cursor_execute's error handling
propagates up through _execute_context.

As part of this change, DBAPI errors raised from within these event
hooks will now be wrapped as SQLAlchemy exceptions.

Fixes: #13381
Change-Id: I6df29406f1eed9c318d02b00b999408c1e83535d