[MERGE #4096 @sigatrev] ARM64: TryFoldConst
[MERGE #4096 @sigatrev] ARM64: TryFoldConst

Merge pull request #4096 from sigatrev:tryconstfold

don't replace a reg opnds with const opnds that won't fit within the same size register

mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore