[1.10>master] [MERGE #5538 @dilijev] OS#17035705: Mark SetItem as JS_REENTRANT in CopyWithinHelper.
[1.10>master] [MERGE #5538 @dilijev] OS#17035705: Mark SetItem as JS_REENTRANT in CopyWithinHelper.

Merge pull request #5538 from dilijev:copywithin-reentrant

Found by OSS-Fuzz

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