[GlobalISel][AArch64] Add instruction selection support for G_FCOS and G_FSIN

This contains all of the legalizer changes from D57197 necessary to select
G_FCOS and G_FSIN. It also updates several existing IR tests in
test/CodeGen/AArch64 that verify that we correctly lower the G_FCOS and G_FSIN
instructions.

https://reviews.llvm.org/D57197
3/3

llvm-svn: 352402