Do not omit the anyFunctionType from intersections

[weswigham]

Fixes #35390

We assume that if getSignatureApplicabilityError produces an error for a non-normal check mode, that under Normal check mode it will as well. In the example given in the issue, getSignatureApplicabilityError under CheckMode.SkipContextSensitive produced an error result, because the onChange property was an intersection type of the anyFunctionType and another type, which, when intersected just became that other type - this, in turn, caused an assignability error. Under Normal mode, the context-sensitive function is checked, and found, when intersected with that type, to satisfy the relationship. Ergo, the correct fix is to preserve the anyFunctionType in intersections (rather than omitting it as though it were an empty object), so its behavior can propagate.