[IMP] tests: add test_sequence order for tests

We have some tests in odoo/upgrade that are sensitive to the order on
which they are executed. Specifically: IntegrityCase tests need to be
run after all UpgradeCase tests across all Odoo modules.

To support this we implemented a sorting mechanism for tests based on
the test_sequence class attribute. This is intended to be used by meta
cases, not by individual tests.

closes odoo/odoo#66521

Related: odoo/upgrade#2184
Signed-off-by: Denis Ledoux (dle) <dle@odoo.com>