This is all of the expected 0.14.0 progress on #21530, which can now be
postponed once this commit is merged.
This required rewriting the (un)wrap operations since the original
implementations were extremely buggy.
Also adds an easy way to retrigger Sema OPV bugs so that I don't have to
keep updating #22419 all the time.
This matches master branch. We can look into adding more target coverage
as we switch to stage2. As it stands, this works around having to
duplicate the "Executor" logic to figure out when to not run the tests
due to them being non-native.
* migrate runtime safety tests to the new test harness
- this required adding compare output / execution support for stage1
to the test harness.
* rename `zig build test-stage2` to `zig build test-cases` since it now
does quite a bit of stage1 testing actually. I named it this way
since the main directory in the source tree associated with these
tests is "test/cases/".
* add some documentation for the test manifest format.
