[llvm][AArch64][Assembly]: Add FDOT2/FDOT4 assembly and disassembly. (#70237)

This patch adds the feature flag FDOT2/FDOT4 and the
assembly/disassembly
for the following instructions of NEON and SVE2:
 * NEON:
   - FDOTlane
   - FDOT
 * SVE2:
   - FDOT_ZZZI_BtoH
   - FDOT_ZZZ_BtoH
   - FDOT_ZZZI_BtoS
   - FDOT_ZZZ_BtoS

That is according to this documentation:
https://developer.arm.com/documentation/ddi0602/2023-09