feat(en): Fix operator address assignment for ENs

[slowli]

What ❔

• Moves fee_account_address from the l1_batches table to the miniblocks table using a combined SQL and programmatic migration.
• Replaces uses of l1_gas_price, l2_fair_gas_price and base_fee_per_gas from l1_batches to the corresponding miniblocks fields. Removes uses of l1_batches.is_finished.
• Updates L1BatchHeader / MiniblockHeader correspondingly.

Why ❔

Currently, operator address is not persisted for miniblocks, but only for L1 batches. This has several negative implications:

• ENs cannot be used to synchronize other ENs since SyncBlock.operator_address they return may be bogus.
• We have nowhere to get the real operator address for gossip-based syncing as well.

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.
• Spellcheck has been run via cargo spellcheck --cfg=./spellcheck/era.cfg --code 1.

[slowli]

The overall migration strategy is as follows:

1. Perform SQL migration changing the DB schema. It should be fast and shouldn't disrupt system operation.
2. Perform programmatic data migration (see fee_address_migration module). This migration is run in the background in the state keeper / EN pod. It relies that step 1 is complete (i.e., data schema is changed).
3. (Will be implemented separately) Perform another SQL migration removing obsolete L1 batch columns.

DB queries are rewritten in a way that they will continue to work after the obsolete L1 batch columns are removed. (The natural exception is migration-specific queries, but they should never run at this point.) I.e., code deployed on step 2 should continue working both before and after completing step 3.

[perekopskiy]

Looks good! Sorry for the long review. Please resolve conflicts and I will reapprove

[RomanBrodetski]

Looks good! Surprized it's that involved though. I don't see how exactly we could do it simpler. But it's a good change and we need experience in migrating large tables.