[NFC] Updating Debug Info generation for 'this' (#119445)
This is PR is updating the debug info generation for `this`. This is
required to fix the generation of debug information for HLSL RWBuffer
type. This was required from another PR:
https://github.com/llvm/llvm-project/pull/119041/files
Co-authored-by: Joao Saffran <jderezende@microsoft.com>
