fix(db): Fix write stalls in RocksDB (for real this time)

[slowli]

What ❔

A previous fix didn't really work judging by Merkle tree behavior on the stage env. This PR makes the initialization timeout configurable (and increases the default value from 10s to 30s; 30s is approximately equal to the compaction duration) and slightly increases the number of retries on stalled writes.

Why ❔

Having write stalls leads to panics and is obviously bad.

Checklist

• PR title corresponds to the body of PR (we generate changelog entries from PRs).
• Tests for the changes have been added / updated.
• Documentation comments have been added / updated.
• Code has been formatted via zk fmt and zk lint.

[slowli]

Couple of other options we might consider:

• Increase the number of level-0 SST files for stopped writes. I feel that it doesn't solve the problem, just postpones it.
• Add a subcommand to rocksdb_util (compact?) that would just create a RocksDB instance and wait indefinitely until its writes are not stopped. This could work well with the main node, but AFAICT, rocksdb_util is currently not shipped with the EN Docker image and making it work there could require some work.

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (0e5eefc) 35.58% compared to head (3345c17) 35.61%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #292      +/-   ##
==========================================
+ Coverage   35.58%   35.61%   +0.03%     
==========================================
  Files         520      520              
  Lines       28336    28357      +21     
==========================================
+ Hits        10084    10100      +16     
- Misses      18252    18257       +5     

Files	Coverage Δ
core/bin/external_node/src/main.rs	0.00% <ø> (ø)
core/lib/config/src/configs/database.rs	69.23% <100.00%> (+2.56%)	⬆️
...lib/zksync_core/src/metadata_calculator/helpers.rs	87.50% <100.00%> (+0.40%)	⬆️
...ore/lib/zksync_core/src/metadata_calculator/mod.rs	88.23% <100.00%> (+0.23%)	⬆️
...lib/zksync_core/src/metadata_calculator/updater.rs	94.25% <100.00%> (+0.03%)	⬆️
core/bin/external_node/src/config/mod.rs	21.42% <0.00%> (-0.80%)	⬇️
core/lib/storage/src/db.rs	51.90% <78.94%> (+4.61%)	⬆️

... and 29 files with indirect coverage changes

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[RomanBrodetski]

Very good, let's keep trying!