consensus: finalize DKG ceremony speculatively

[SuperFluffy]

Describe the feature

Finalization of DKG ceremonies should happen speculatively and only on request from the application. Further, this construction should not end the ceremony: in case validators do not agree on the same outcome, this leaves the option to process more finalized blocks in the meantime.

Right now, the DKG ceremony is finalized on the pre-to-last finalized block of an epoch to be included in the last block of that epoch. This is problematic: when constructing a proposal on top of some parent, simplex only guarantees that the parent is notarized, not finalized.

Related: #565, https://github.com/commonwarexyz/monorepo/pull/2214

Additional context

No response