libsql-wal final integration

[MarinPostma]

This PR wires most of libsql-wal related stuff into sqld, and fixes uncovered bugs along the way.

what works:

• primary, replicas and schema using the new wal. Replication only works with storage enabled
• s3 storage
• embedded replicas (untested yet)

The new wal exists side by side with the legacy wal. To enable it, pass the --use-custom-wal libsql-wal arg. Bottomless configuration remains unchanged.

what doesn't work yet:

• forking
• some quirks with the replication index (will fix as a followup)
• replica checkpointing
• replication without bottomless enabled
• automatic restore

[MarinPostma]

thanks @LucioFranco will address all the comments in followups