Fix issue 11051 - Unmatched case in a final switch should throw in both release and non-release mode

[ntrel]

Reboot of #6095 so far just fixing merge failure.

Keep a HALT instruction in a final switch statement if the function is @safe and -release mode is enabled.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	11051	major	Unmatched case in a final switch should throw in both release and non-release mode

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#14841"

[AndrejMitrovic]

Thanks @ntrel, I'll close the other PR.

[ntrel]

The tests were all passing except circleci found 2 core dump files, see:
https://app.circleci.com/pipelines/github/dlang/dmd/24135/workflows/50b27a55-a64d-464c-a01e-1f8d354c7450/jobs/51690

So I have disabled generating core dumps with ulimit.