Turns out there were some subtle internal bugs discovered by the just
added `tests/devx/test_tooling::test_crash_handler_cms` suite.
So this fixes,
- a mis-ordering around `rt_repl_fixture :=` in the logic of
`DebugStatus.maybe_enter_repl_fixture()`.
- `.devx.debug._post_mortem._post_mortem()` ensuring we now **always**
call `DebugStatus.release()`, and thus unwind the exist-stack managing
the `repl_fixture` exit/teardown, **even in the case** where
`yield False` is delivered from the user-fixture-fn (meaning
`dnter_repl=False`) thus triggering an early `return` (as is done in
the new test suite).
f5056cdd02