[clang] [CIR][AArch64] Lower vfma lane builtins (PR #188190)

[Yair Ben Avraham via cfe-commits]

yairbenavraham wrote:

@banach-space  I’m wondering, not sure, about the scalar `f16` CIR coverage here.
The moved scalar file covers the LLVM path, but enabling the full `-fclangir` run for all scalar forms still hits an unrelated `Poly128` CIR NYI before the file completes. I therefore kept CIR/CIRLLVM coverage for the supported scalar `f32`/`f64` forms, but not for scalar `f16`.
Shall I keep that split in this PR, or should I try to address/work around the unrelated `Poly128` CIR failure as follow-up so the scalar `f16` forms can also be verified through CIR?

https://github.com/llvm/llvm-project/pull/188190