[llvm] [DebugInfo][DWARF] Add heapallocsite information (PR #132073)

[via llvm-commits]

thejh wrote:

The [DWARF v6 working draft](https://snapshots.sourceware.org/dwarfstd/dwarf-spec/latest/dwarf6-20250707-1422.pdf) now contains this feature as `DW_AT_alloc_type` with ID 0x96.

Which makes me wonder - would you prefer to directly use the ID from the draft standard in LLVM, or would you prefer to use an ID in LLVM-private ID space until the standard is actually finalized?

https://github.com/llvm/llvm-project/pull/132073