[AArch64][Clang] Refactor code to emit SVE & SME builtins (#70662)
This patch removes duplicated code in EmitAArch64SVEBuiltinExpr and
EmitAArch64SMEBuiltinExpr by creating a new function called
GetAArch64SVEProcessedOperands which handles splitting up multi-vector
arguments using vector extracts.
These changes are non-functional.
