QA WAR - _serializedValidationGUID field

[cdhanna]

For Unity 6000.3, the _serializedValidationGUID field was added, but why ?
At min, we should hide this in the inspector. At best, we should understand why it was added.

[DiasAtBeamable]

Upon further searching, I've found that _serializedValidationGUID is being used to save the GUID string for later usage after recompiling or domain reload. Then, it sets the ValidationGuid to the serialized value so it can keep track of the same GUID. I just added the HideInInpector attribute to it.
Fixed in commit: eb22a22