chore: committor service needs to cleanup pending lookup tables

[thlorenz]

When the validator is stopped but some lookup tables were still in use then those are not deactivated nor closed.

Since it takes a few seconds to be able to close deactivated lookup tables we need to find a way to perform this via a separate tool. The process could be as follows:

• lookup tables are tracked as part of the committor service sqlite db
• once they are successfully deactivated and closed that row is removed

Once a validator is stopped, a separate tool can read those entries from the DB (which is part of the ledger) and deactivate all those tables and then close them.

For validator restart we need to be more careful to identify which tables we can close (distinguishing tables created before restart from those created after). If we store the ephemeral slot at which they were created we can use that in the tool, i.e. close all tables up to slot x

[thlorenz]

This has been solved mostly as part of #366.
Pubkeys in lookup tables are refcounted and when a lookup table is no longer needed it is deactivated and later closed.

What is not implemented yet is the script to find and close lookup tables that stayed open when the validator shutdown, thus I'm leaving this open for now.