[Java][Spring] fix unhandledException not working in combination with…

Fixes #4393 (closed) JavaSpring template by taking configuration options skipDefaultInterface and unhandledException into account simultaneously properly.

unhandledException is no longer dependent on skipDefaultInterface as it is applicable to all java versions and implementations independent from abstract classes, interfaces or interfaces with default implementations.

Added additional samples to verify this change and existing samples didn't get touched by it:

e.g.

ResponseEntity<Void> addPet(@ApiParam(value = "Pet object that needs to be added to the store" ,required=true )  @Valid @RequestBody Pet body);

becomes

ResponseEntity<Void> addPet(@ApiParam(value = "Pet object that needs to be added to the store" ,required=true )  @Valid @RequestBody Pet body) throws Exception;

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