PEP-734 has been accepted (for 3.14).
(FTR, I'm opposed to putting this under the concurrent package, but
doing so is the SC condition under which the module can land in 3.14.)
* Ensure that destructors are called in the test that created interpreters, not after finishing it.
* Try to create/run interpreters in threads simultaneously.
* Mark tests that requires over 6GB of memory with bigmemtest.
This approach eliminates the originally reported race. It also gets rid of the deadlock reported in gh-96071, so we can remove the workaround added then.
