Save sync configuration

[sivukhin]

This PR saves additional data in the metafile for sync:

{
  ...
  "saved_configuration": {
    "remote_url": "http://localhost:31420",
    "partial_sync_prefetch": null,
    "partial_sync_segment_size": null
  }
}

This data is used only to preserve some configuration on disk and allow client to not store this anywhere else.
So, for example, in agentfs case, user will init db with some parameters once and then it can use it easily be providing only auth token.

[turso-bot]

Please review @jussisaurio