Move sync tables from public to ponder_sync schema

[0xOlias]

I manually tested these scenarios on an example app locally:

1. Run app using old schema (0.2.2), then start app again using new schema
2. Run app using old schema at an older migration level (0.1.8), then start app again using new schema
3. Run app from scratch using new schema
4. Run app from scratch using new schema, then downgrade to old schema, then upgrade again to new schema