* Destructuring declaration prefers type annotation type
Previously, getTypeForBindingElement would always union the declarations type and
the type of the default initializer. Now, if the declaration has a type
annotation, it does not union with the initializer type. The type
annotation's type is the one used.
* Small cleanup in parentDeclarationHasTypeAnnotation
* Refactoring based on PR comments
* Combine getCombined*Flags into a single helper function
Retain the individual functions since they are used a lot.
* Remove unneeded temp
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