[clang] [CIR][AArch64] Lower vfma and scalar FMA lane builtins (PR #204819)

[Andrzej Warzyński via cfe-commits]

https://github.com/banach-space approved this pull request.

LGTM, thank you!

I've left one nit :) Thank you for the additional clean-up (e.g. in `getNeonType`) and for sending your changes in separate (and well documented) commits. Neatly done!

Is there anything left?

https://github.com/llvm/llvm-project/pull/204819