We seem to have some redundancy with "e2e" and "unit tests"

[GalRogozinski]

          We seem to have some redundancy with those tests...

Both QBFT and types/partialSig tests pretty much concentrate on the outer-wrapper msg.Validate() function and pretty much test the same thing.

In ssv with the MsgProcessingSpecTest we pretty much do the same checks all over again, just in the context of the entire processing.

We need to have a discussion on how we do this properly...
Do we want to have those MsgSpecTest check all the validation cases and have another test that proves that the Validate function is called?
Maybe we can have only MsgProcessingTests?

Originally posted by @GalRogozinski in #441 (comment)