Add additional tests to the `History` mechanism

[iamrecursion]

What should be done?

Not for this PR, but it may be good to add some tests against the Smt. For example,

• Create an Smt.
• Update it and use the returned mutation set to create a history overlay.
• Query the overlay for some nodes, and make sure they are the same as in the original Smt

We can add these tests once more of the functionality is flashed out.

From #679.

How should it be done?

As above.

When is this task done?

When the additional tests have been implemented.

Additional context

No response

[Himess]

Can i take ?

[huitseeker]

@Himess Sure!

[huitseeker]

Note: there's a type gap here: MutationSet.node_mutations() gives Map<NodeIndex, NodeMutation> (with Addition(InnerNode) or Removal), but History.add_version() wants NodeChanges which is Map<NodeIndex, Word>. Similarly for leaves, MutationSet.new_pairs() is flat key-value pairs while LeafChanges groups them by LeafIndex into CompactLeaf maps.

[iamrecursion]

I should also note that the History API may be subject to some small amount of changes as it evolves with the work on the new SMT forest.