[1.8>1.9] [MERGE #4633 @MikeHolman] add some asserts during jit handshake
[1.8>1.9] [MERGE #4633 @MikeHolman] add some asserts during jit handshake

Merge pull request #4633 from MikeHolman:addasserts

Well behaved programs should never hit these paths, so add early asserts to catch bugs early in testing

OS: 15490382

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