Add flags to generate zkApp transactions carrying events, actions and several account updates

The `update-state` subcommand of the zkApp test transaction tool previously always produced transactions with empty events and actions and a single account update. It now accepts `--num-events`, `--num-actions`, `--event-elements-per` and `--action-elements-per` to fill those arrays, `--repeat-arrays` to emit identical arrays rather than distinct ones, and `--num-account-updates` to repeat the update within one transaction. This makes it possible to generate the heavy zkApp payloads needed to exercise and load-test archive nodes.

The two count flags also accept `max`, which fills up to the network's event and action limit, so the same command line can be reused against networks whose limits differ. Omitting all of the flags leaves the generated transaction unchanged.
