chore: adding compaction on DB open

[Freyskeyd]

Description

Adds a manual compaction when opening the DB on pending_pool and precedence_pool CF

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[dvdplm]

I'm ok doing this, but there's a risk here: on a big rocksdb, doing compaction can take a long time and afaik there is no way to know just how long it takes.

We can mitigate this risk by making it optional by way of a config option, or have a subcommand that does the compaction while the node is running (this is safe because rocksdb runs compactions on its own whenever it wants to).