Fix Prepare/Process Proposal state access

[evan-forbes]

currently, we're using a bit of a hack for state access in process/prepare proposal, where we're using a query sdk.Context instead of each managing their own forks of the state. We will need to switch to something that is more similar to what is occuring in v0.47.x of upstream. We might also have to make a modification that allows us to call Prepare/ProcessPropsosal on heights == 1, since our fork of comet does that