Embedded LND: migrate to SQLite

[kaloudis]

https://github.com/lightningnetwork/lnd/issues/9964

Potential effects:

• Smaller DB size
• Faster start-up
• Faster graph sync
• Better performance
• Enables https://github.com/ZeusLN/zeus/issues/1948

Other work required:

• Update speedloader code
• Determine if there's a db migration path or if this will be just be for newly created wallets

[Darth-Coin]

I think the migration part should be only for new nodes, just to avoid possible issues. Optional could be included a migration script for those that want to move an old node from one device to another. If old node was created on old db, then migrate to SQlite first. If is already on SQLite, just do the backup/migration.