[Clang] Extend EmitPseudoVariable to support debug records (#94956)

CGDebugInfo::EmitPseudoVariable currently uses detailed logic to exactly
collect llvm.dbg.declare users of an alloca. This patch replaces this
with an LLVM function for finding debug declares intrinsics and also
adds the same for debug records, simplifying the code and adding record
support.

No tests added in this commit because it is NFC for intrinsics, and
there is no way to make clang emit records directly yet - one of the
existing tests however will switch to covering debug records once
https://github.com/llvm/llvm-project/pull/89799 relands.