Connect resharding finish operation

[timvisee]

Tracked in: #4213
Depends on: #4507

When the resharding driver is done, properly end resharding and clean things up.

This is one of the necessary changes we need to complete a resharding operation front to end. I'd like this so we can start testing with it soon.

Tasks

• Merge Commit read/write hashrings while resharding #4507
• Rebase onto dev
• Undraft PR

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[timvisee]

This is here until we propose hash ring changes through consensus in the driver. That'll be in a separate PR.

[ffuugoo]

I don't like it, but OK. 😂

Though, I'd structure finish_resharding like this:

    pub fn finish_resharding(&mut self, resharding_key: ReshardKey) -> CollectionResult<()> {
        // TODO(resharding): don't commit resharding here, commit through consensus in driver
        self.commit_write_hashring(resharding_key.clone())?;

        self.check_resharding(&resharding_key, |_| {
            // TODO(resharding): Check resharding is in the correct state to finish resharding!
            Ok(())
        })?;

        self.resharding_state.write(|state| {
            state.take();
        })?;

        Ok(())
    }

I.e., put commit_write_hashring call before check_resharding.

[timvisee]

put commit_write_hashring call before check_resharding.

Then it panics due to surrounding checks.

We can also implement the consensus calls for setting resharding states first, because then we don't have to do this.

[timvisee]

I moved this on top of #4507 so that we don't need the temporary 'commit write' hack anymore.

This now just connects the finish resharding consensus message.