fix(ledger): running out of disk space due to cleanup service not cleaning anything

[dnut]

Fix

The cleanup service is supposed to delete data from the ledger from very old slots. It also refuses to delete data from unrooted slots, since we definitely need those slots.

Since we don't have consensus, we have no way to know which slots are rooted. So the cleanup service is just assuming no slots are rooted, and likewise isn't cleaning up anything. That means we will eventually run out of storage on any server.

I added an assumption that anything over 100 slots old is rooted. It's not a perfectly safe assumption because you really need consensus to be sure about this. So we'll fix this when consensus is done. But for now we need some kind of basic assumption here so the validator can function without crashing the entire server.

A slot typically becomes rooted after 32 slots pass. The probability of passing 100 slots without being rooted is extremely unlikely and would only happen in the event of a massive consensus failure. This is a reasonable assumption to live with for the time being, until we have consensus.

I also increased the number of shreds to allow before cleaning them up. Previously the limit was 1,000 which could represent only a few slots. This configurable basically means we delete all rooted slots. I bumped this up to 5 million shreds. This means the ledger will use about 10-20 GB of storage space once it reaches the limit, and it should contain shreds going back for roughly an hour. Later we'll likely need to make this larger so replay can catch up from snapshots more reliably, or configurable so RPC can serve arbitrarily old data. For now, while the shreds are not actually used for anything, I'm keeping it more conservative to minimize hardware requirements.

Test and RocksDB upgrade

To satisfy test coverage requirements I needed to add a unit test for cleanBlockstore. This test wouldn't work without flushing the data_shred column family. This required changes to rocksdb-zig to add flush. So those upgrades are also included in this pr.

[codecov]

Codecov Report

Attention: Patch coverage is 96.22642% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/ledger/cleanup_service.zig	96.66%	1 Missing ⚠️
src/utils/collections.zig	94.73%	1 Missing ⚠️

Files with missing lines	Coverage Δ
src/ledger/database/hashmap.zig	91.66% <ø> (ø)
src/ledger/database/interface.zig	99.72% <ø> (ø)
src/ledger/database/rocksdb.zig	95.74% <100.00%> (+0.12%)	⬆️
src/utils/interface.zig	100.00% <ø> (ø)
src/ledger/cleanup_service.zig	91.78% <96.66%> (+7.57%)	⬆️
src/utils/collections.zig	93.98% <94.73%> (-0.16%)	⬇️

... and 2 files with indirect coverage changes