SQLite 3.26 repoints foreign key constraints on table renames even when
foreign_keys pragma is off which breaks every operation that requires
a table rebuild to simulate unsupported ALTER TABLE statements.

The newly introduced legacy_alter_table pragma disables this behavior
and restores the previous schema editor assumptions.

Thanks Florian Apolloner, Christoph Trassl, Chris Lamb for the report and
troubleshooting assistance.

Co-Authored-By: Xavier Fernandez <xavier.fernandez@polyconseil.fr>

Thanks Taqi Abbas and Raphael Kimmig for the report.

There are test failures with older versions.

Reverted "Fixed #25251 -- Made data migrations available in TransactionTestCase when using --keepdb."

This reverts commits b3b1d3d4 and
9fa0d378 due to reverse build failures
for which a solution isn't forthcoming.

Co-authored-by: Tim Graham <timograham@gmail.com>

Seems to be a needless restriction in
978a00e3.

Refs #25251 -- Filtered out skipped tests when processing the test suite to set _next_serialized_rollback.

Co-Authored-By: Hasan Ramezani <hasan.r67@gmail.com>

Thanks Mariusz for suggesting it.

Thanks Tim Graham for the review.