[clang] [Clang](NFC) Add coverage for VTable debug info (PR #151818)

[Tomohiro Kashiwada via cfe-commits]

kikairoya wrote:

> Just a minor point: the original tests assumed normal debug info generation. Now they use `-debug-info-kind=limited -dwarf-version=5 -O1`. Can we run the tests with the original options and the new ones? Any specific reason for the options change?

I thought `-disable-O0-optnone -disable-llvm-passes` are rarely used in practice, so I wanted the tests to run with more common options. That said, I realize I probably should have used `-O0` instead of `-O1`.
Also, since there are cases where the results differ between `-O0` and `-O1`, I'll add tests with `-O0` as well, as you said.


https://github.com/llvm/llvm-project/pull/151818