Clean up overlong function `handle_finalized_block` in DKG actor

[SuperFluffy]

Describe the bug

handle_finalized_block in the DKG actor has close to 200 lines and is painful to read. Worse, there is an early return in the middle of it, which is hard to see.

Clean up the function body to make it easier to understand what's going on.

1:

tempo/crates/commonware-node/src/dkg/manager/actor/mod.rs

Line 622 in ed3c639

async fn handle_finalized_block<TStorageContext, TSender>(

2:

tempo/crates/commonware-node/src/dkg/manager/actor/mod.rs

Line 704 in ed3c639

return Ok(None);

Steps to reproduce

N/A

Logs

Platform(s)

No response

Container Type

Not running in a container

What version/commit are you on?

ed3c639

If you've built from source, provide the full command you used

No response

Code of Conduct

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