Add option to serve historical SPDD and DRDD to AccountsState

[sandtreader]

Add a config option to AccountsState to offer historical SPDD and DRDD for each epoch

/spdd?epoch={n}
/drdd?epoch={n}

[whankinsiv]

I opened this PR in Caryatid to add query parameter support and got most of the historical SPDD and DRDD implementation done today.

I noticed that the accounts state is stored as StateHistory::<State>::new("AccountsState") and it does not make sense to store the distribution history in multiple states simultaneously.

For now I've created a new DistributionHistory struct that has params inserted at the end of each epoch separately. Any objections to this approach?

[sandtreader]

There's another way to do this which I've used in AccountsState for the snapshots - wrap it in an Arc and then when the State gets cloned your part of it will be shared rather than copied.

I'll release Caryatid update today - the CI just triggers on version changes so feel free to include version bumps in the PRs.

[whankinsiv]

Added in #110.