Track "Update operations commit-reveal chain may lead to an unresolvable DID"

[BenjaminMoe]

decentralized-identity/sidetree#1169

Quote:  @shakreiner
The current iterations over Update operation using the commit-reveal chain may lead to an infinite loop when trying to resolve a DID.
The thing that can cause this state is having a DID with 2 Update operations, where the second operation commits to the first one again.
This situation should not be allowed based on the specification (updateCommitment must be a new commitment in every operation), but the code doesn't seem to enforce that.

As a sidetree implementation, we need to make sure that this is working in-code and not just in-theory. We need to add a unit test that tracks multiple-commits to make sure it doesn't result in an unsolvable did, and formulate a response depending on the unit test.