[clang][DebugInfo][test] Move debug-info tests from CodeGenCXX to DebugInfo directory (llvm#154538)

This patch works towards consolidating all Clang debug-info into the
`clang/test/DebugInfo` directory
(https://discourse.llvm.org/t/clang-test-location-of-clang-debug-info-tests/87958).

Here we move only the `clang/test/CodeGenCXX` tests. I created a `CXX`
subdirectory for now because many of the tests I checked actually did
seem C++-specific. There is probably overlap between the `Generic` and
`CXX` subdirectory, but I haven't gone through and audited them all.

The list of files i came up with is:
1. searched for anything with `*debug-info*` in the filename
2. searched for occurrences of `debug-info-kind` in the tests

There's a couple of tests in `clang/test/CodeGenCXX` that still set
`-debug-info-kind`. They probably don't need to do that, but I'm not
changing that as part of this PR.

(cherry picked from commit f2aedc2)

Author: Michael137