jetstreamer-source: use firehose StatsTracking for progress logging

[senzenn]

The handler kept its own blocks_processed: AtomicU64 just to log progress every 10k blocks, while firehose() already tracks all of this and we were passing stats_tracking: None.

• new stats_interval_slots config field (default 10000, 0 disables)
• register a StatsTracking callback that logs slots/blocks/transactions/entries/leader-skipped + tps; the callback fires per worker thread so thread_id is included
• drop the atomic counter and its two logging sites
• add --stats-interval-slots to the jetstreamer example

Tested against the old-faithful archive (50 slots of epoch 885, interval 10):

Firehose progress thread_id=0 slots=11 blocks=11 transactions=12435 entries=9535 leader_skipped_slots=0 tps=2902
Firehose progress thread_id=2 slots=24 blocks=24 transactions=27338 entries=20563 leader_skipped_slots=0 tps=417
Firehose progress thread_id=1 slots=47 blocks=47 transactions=53267 entries=33296 leader_skipped_slots=0 tps=3578

[kespinola]

Suggested change

	let stats_tracking = (config.stats_interval_slots != 0).then_some(
	jetstreamer_firehose::firehose::StatsTracking {
	on_stats: log_firehose_stats,
	tracking_interval_slots: config.stats_interval_slots,
	},
	);
	let stats_tracking = config.stats_interval_slots.map(|tracking_interval_slots| {
	jetstreamer_firehose::firehose::StatsTracking {
	on_stats: log_firehose_stats,
	tracking_interval_slots,
	}
	});

If go as optional can use a map and the None to signal that logging should be disabled.

[senzenn]

.map needs the field to be Option<u64> (it's u64 right now), and the != 0 check is load-bearing — upstream does slot % tracking_interval_slots unguarded ([firehose.rs:1575](https://github.com/rpcpool/yellowstone-vixen/blob/main/crates/jetstreamer-firehose/src/firehose.rs#L1575)), so a 0 has to become None or it panics. A plain .map passes Some(0) straight through and brings the panic back.

Happy to move to Option<u64>, just keeping the guard:

let stats_tracking = config
    .stats_interval_slots
    .filter(|&n| n != 0)
    .map(|tracking_interval_slots| jetstreamer_firehose::firehose::StatsTracking {
        on_stats: log_firehose_stats,
        tracking_interval_slots,
    });

Want it opt-out (default Some(10_000)) or opt-in (default None)? I'll fix up the defaults and tests to match.

[kespinola]

Do we have to return a future or can the function be made async and passed as the callback?

[senzenn]

Has to be a boxed future upstream's Handler<Data> trait requires Fn(usize, Data) -> BoxFuture<'static, HandlerResult>, so a bare async fn won't satisfy the bound. .boxed() erases the opaque future into the BoxFuture it expects.

Same shape as the existing on_block/on_tx/on_entry callbacks at lib.rs:663–681. Happy to inline it as a closure next to those if you'd prefer.