SQLite WAL files are not truncated in signer and aggregator

[jpraynaud]

Why

The WAL files produced by SQLite are constantly growing whereas the should be truncated automatically:

• Example file size on release-mainnet:

174604288 aggregator.sqlite3
327680 aggregator.sqlite3-shm
163390992 aggregator.sqlite3-wal

• Example file size on testing-mainnet:

31645708288 cardano-transaction.sqlite3
425984 cardano-transaction.sqlite3-shm
30943029312 cardano-transaction.sqlite3-wal

What

Make the WAL files automatically truncated.

How

For signer & aggregator add a (repeating?) task that:

• Execute the command PRAGMA wal_checkpoint(SQLITE_CHECKPOINT_TRUNCATE);
• Vacuum the databases ? (not the cardano_transaction database on aggregator as it can be very large).
• Maybe handle the connections to the database differently to allow for truncating the WAL file when the connection is refreshed?