[Proposal] Add validation tooltip message to ALL fields

[GogoVega]

@knolleary, @dceejay,
To generate the tooltip there are two possibilities:

1. In typedInput validate and the returned value is a boolean
2. In validateNodeEditorProperty but the validate function (PR#4455) must return a string

The advantage of the second is that it's centralized, the disadvantage is for backward compatibility. What is the best approach?