proposers submit proof claims

[just-mitch]

A proposer should be able to see if it is in the proof claim period and then "decide" whether it wants to submit a proof claim.

We will create a module to control that decision-making. Presently, it will simply return true (the optimistic case where the pending chain can be proven).

In practice, we expect implementations to be more intelligent and check that the proposer itself has at least seen/verified the data needed to produce the proofs.

The proposer must have a separate module for getting a Quote which is required to claim a proof. The default implementation here will be to generate a quote from itself. In practice, this would be the case if a prover marketplace is running a proposer/validator.

In practice, we expect most proposer to run with a separate implementation described here #8577