Skip expression-based index reflection for SQLite

Skip expression-based index reflection for SQLite

Reflection of an index based on SQL expressions are now skipped with a
warning, in the same way as that of the Postgresql dialect, where we currently
do not support reflecting indexes that have SQL expressions within them.
Previously, an index with columns of None were produced which would break
tools like Alembic.

Fixes: #4431
Change-Id: I1363ade912d206b42669331e2be2bb6f444b65a2
(cherry picked from commit 08994cb97c501a3cf984fd827eba9aa9614b9dd3)