- changes the code implementation to "the maximum number of consecutive unused addresses" in esplora async and blocking extjensions. - treat `stop_gap = 0` as `stop_gap = 1` for all purposes. - renames `past_gap_limit` to `gap_limit_reached` to indicate we want to break once the gap limit is reached and not go further in `full_scan`, as suggested in https://github.com/bitcoindevkit/bdk/issues/1227#issuecomment-1859040463 - change the tests according to the new implementation. - add notes on what `stop_gap` means and links to convergent definition in other Bitcoin-related software. Closes #1227