Add ambiguous column support to SimpleResultMetaData

Add ambiguous column support to SimpleResultMetaData

Fixed issue where :meth:`.Result.freeze` would lose track of ambiguous
column names present in the original :class:`.CursorResult`, causing
key-based access on the thawed result to silently return a value instead of
raising :class:`.InvalidRequestError`.  The
:class:`.SimpleResultMetaData` now accepts and propagates ambiguous key
information so that frozen, thawed, and pickled results raise consistently
for duplicate column names.  Pull request courtesy Saurabh Kohli.

Fixes: #9427
Closes: #13335
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/13335
Pull-request-sha: c03904ece298493ca69bf6e9cbdae23c7fb6a7b0

Change-Id: Ia184f77b442b069e6f9a4f94a967ead41a1704b6