Reclaims more old accounts in clean

[brooksprumo]

Problem

In clean_accounts(), if there are old storages and old accounts beyond what is expected, we do not always reclaim them. This is because when scanning the candidates during clean, if the account's latest slot in the slot list is not in the uncleaned_roots list, we don't collect reclaims.

This can happen if there are candidates from old/ancient slots, where their newest entry is in a slot that is not being visited by clean. We would find multiple entries for this candidate in the index, yet determine not to collect reclaims.

Summary of Changes

Collect reclaims on candidates that have slot lists greater than one entry, and if they are all cleanable (i.e. rooted).

[jeffwashington]

this looks correct. This seems like we can explain now why the brute force method wasn't working, too. And, since we were handling duplicates on the index correctly when we were starting with the in-mem index only. This seems correct.

[HaoranYi]

Nice find.
looks correct to me.

[brooksprumo]

I spun up a mnb node with the disk index disabled to see how it performed. Here's some results:

clean always has a lot of work to do on the first iteration. And we see it removing the old slots:

And since we're cleaning up reclaims, shrink can do a better job now too, purging lots of zero lamport accounts: