[llvm] [RISCV] Add list of supported profiles to -print-supported-extensions (PR #90757)

[Alex Bradbury via llvm-commits]

https://github.com/asb approved this pull request.

LGTM. I agree there's not much point elaborating the full ISA string for each one.

This patch is making me realise that we've probably erred in not gating the not-yet-ratified and subject-to-change rvb*, rvm* and rva23* profiles in some way.

https://github.com/llvm/llvm-project/pull/90757