[llvm] [DirectX] Add ObjectFile boilerplate for objdump (PR #151434)

[Justin Bogner via llvm-commits]

https://github.com/bogner commented:

This is great. Makes debugging shader flags as simple as `llvm-objdump --section=SFI0 -s` and should be helpful for root signatures as well.

A few comments on the error handling strategy for things that don't exist in the format, but generally this looks good.

https://github.com/llvm/llvm-project/pull/151434