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

[David Blaikie via cfe-commits]

dwblaikie wrote:

Yeah, I think it's worth still keeping some language grouping - language features are somewhat hard to just grep for, so having some grouping may help find any existing coverage for a feature so we don't just keep adding new files.

( clang/test/DebugInfo/CXX/Inputs/debug-info-class-limited.cpp could be renamed to drop the `debug-info` prefix)

https://github.com/llvm/llvm-project/pull/154538