Add more defensive exceptions

[abergs]

We pass a lot of the "Expect failure" tests in the conformance tool, e.g:

But it's often because of null reference etc. Might be better for a library consumer if we threw more precise exceptions.

[aseigler]

Put in a good amount of this.

[abergs]

Do we have many more to add or should we go ahead and close? (unable to run the testing tool for a couple of days)

[aseigler]

I have a few more, then it's mostly fixing cert and sign parsing issues for all the data samples.

[aseigler]

Attestation code is fairly well defended now, with the exception of certificate parsing.

[abergs]

I think we should go ahead and close this now. Please reopen if you deem necessary.