#4082 add mutable accessors to QuorumProposalWrapper

[pls148]

Closes EspressoSystems/espresso-network#2595

This PR:

• Adds mutation methods on QuorumProposalWrapper
• Addresses a missed comment from #4093 add epoch and friends to commitments of new x2 objects #4094

This PR does not:

Key places to review:

[jparr721]

Curious, why bother adding mutable and immutable accessors when we could just make all the fields pub? Seems like this is just adding indirection.

[bfish713]

Yeah I feel like all these fields do not need mutable access

[ss-es]

I think it's not clear we need all of these, but no objection from me

I think QuorumProposalWrapper is really a HotShot-internal type, and it makes sense to me to leave the fields private (or pub(crate) at most)

[pls148]

The main driver here is espresso-sequencer and marketplace-builder-core needing to poke around at the internals of this structure and making it hard to move things around later. Specifically, they have to reference things like proposal.data.proposal.view_number to make changes, (almost?) entirely in their tests. When replacing QuorumProposal2 (which had these fields available at proposal.data.view_number) I had to make a ton of changes to to these repos when the intent of the code wasn't changing. That seems like it creates an unnecessary lock-step for change.

This may end up becoming irrelevant when we move to a monorepo though.