[AArch64][SVE] Add patterns to generate FMLA/FMLS/FNMLA/FNMLS/FMAD

Adjust generateFMAsInMachineCombiner to return false if SVE is present
in order to combine fmul+fadd into fma. Also add new pseudo instructions
so as to select the most appropriate of FMLA/FMAD depending on register
allocation.

Depends on D96599

Differential Revision: https://reviews.llvm.org/D96424