backport stable branch and some vreg cleanups:
* move initialization_completed from cwvreg to base VRegistry class
allowing simplification of CWVregistry
* cleanup initialization process: __registered__ is now called after
initialization completed, by the relevant registry.
* fix/remove deprecated tests
fix security issue #36564 (integrity error w/ RQLUniqueConstraint) by using a global lock serializing commit when some RQLUniqueConstraint is encountered.