Merge pull request dotnet/coreclr#8711 from sivarv/simdAbsOpt

Accelerate Abs intrinsic even in cases where there is no direct instruction support available.

Commit migrated from https://github.com/dotnet/coreclr/commit/9202ba5b7bbd92e53c560882887aaffba4ae5a15

diff --cc src/coreclr/src/jit/compiler.h
Simple merge

diff --cc src/coreclr/src/jit/gentree.cpp
Simple merge

diff --cc src/coreclr/src/jit/rationalize.cpp
Simple merge