Reapply "[Sema] Fix crash on invalid code with parenthesized aggregate initialization" (#76272)

With updates the libc++ tests.

This reverts commit 2205d233 and relands
86dc6e15 and
7ab16fb5.

Original commit was reverted because of failing libc++ tests, see #76232 for
the discussion.

The errors in the tests are spurious in the first place (coming from initialization
of invalid classes), so update the tests to match new behavior that does
not show those errors.