Using unittest.TestCase doesn't work properly when we perform db
queries. Moreover introspection is extremely slow on Oracle without
limiting models to a "backends" app.
Follow up to 8bcca47e83.
The sql_flush() positional argument sequences is replaced by the boolean
keyword-only argument reset_sequences. This ensures that the old
function signature can't be used by mistake when upgrading Django. When
the new argument is True, the sequences of the truncated tables will
reset. Using a single boolean value, rather than a list, allows making a
binary yes/no choice as to whether to reset all sequences rather than a
working on a completely different set.
