[clang] [llvm] [APFloat] Add support for f8E3M4 IEEE 754 type (PR #99698)

[Thomas Raoux via cfe-commits]

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

I'm not particularly familiar with this format but the changes look reasonable and consistent with the other formats. LGTM

https://github.com/llvm/llvm-project/pull/99698