calculate warnings stacklevels dynamically

calculate warnings stacklevels dynamically

A new approach has been applied to the warnings system in SQLAlchemy to
accurately predict the appropriate stack level for each warning
dynamically. This allows evaluating the source of SQLAlchemy-generated
warnings and deprecation warnings to be more straightforward as the warning
will indicate the source line within end-user code, rather than from an
arbitrary level within SQLAlchemy's own source code.

Fixes: #6241
Change-Id: I9ecf3b3ea77424d15e8d4c0aa47350602c0568d7