[llvm] Add initial support for SPE brstack format (PR #129231)

[Ádám Kallai via llvm-commits]

kaadam wrote:

@aaupov @paschalis-mpeis Just one more thing. If you all find the change appropriate, may I ask one fo you to merge the PR at the final stage? I have no permission to do that. Thank you.

https://github.com/llvm/llvm-project/pull/129231