refactor(chain)!: impl sqlite for ConfirmationBlockTime anchored changesets

refactor(chain)!: impl sqlite for ConfirmationBlockTime anchored changesets

We want to not depend on serde_json. If we keep it around for
serializing anchors we won't be able to remove it in the future because
it will always be needed to do migrations.
Currently there is only one widely used anchor, ConfirmationBlockTime.

The desicion was to constrain support to just be for a single anchor
type ConfirmationBlockTime. The anchor table will represent all fields
of ConfirmationBlockTime, each one in its own column.

The reasons:

- No one is using rusqlite with any other anchor type, and if they are,
  they can do something custom anyway.
- The anchor representation may change in the future, supporting for
  multiple Anchor types here will cause more problems for migration
  later on.