smite: retry mine_block_including on mempool eviction

[NishantBansal2003]

Closes: #237

mine_block_including snapshots the mempool and passes the txids to generateblock. If the target RBF fee-bumps a transaction between the two calls, generateblock fails with not in mempool.

Retry with a fresh mempool snapshot up to 3 times. RBF replacement is atomic, so a single retry should succeed. The extra attempt is a buffer.

[morehouse]

style nit:

Suggested change

	for attempt in 1..=MAX_ATTEMPTS {
	let mut txs = self.get_raw_mempool();
	txs.extend_from_slice(private_mempool);
	let txs_json = serde_json::to_string(&txs).expect("tx list serializes to valid JSON");
	let gen_out = self
	.run()
	.arg("generateblock")
	.arg(address.to_string())
	.arg(&txs_json)
	.output()
	.expect("bitcoin-cli generateblock should not fail");
	if gen_out.status.success() {
	return;
	}
	// Only retry if a snapshotted transaction left the mempool (e.g.
	// replaced by an RBF fee bump) before the block was generated.
	let stderr = String::from_utf8_lossy(&gen_out.stderr);
	assert!(
	stderr.contains("not in mempool") && attempt < MAX_ATTEMPTS,
	"bitcoin-cli generateblock failed: {stderr}"
	);
	}
	for attempt in 0..MAX_ATTEMPTS {
	let mut txs = self.get_raw_mempool();
	txs.extend_from_slice(private_mempool);
	let txs_json = serde_json::to_string(&txs).expect("tx list serializes to valid JSON");
	let gen_out = self
	.run()
	.arg("generateblock")
	.arg(address.to_string())
	.arg(&txs_json)
	.output()
	.expect("bitcoin-cli generateblock should not fail");
	if gen_out.status.success() {
	return;
	}
	// Only retry if a snapshotted transaction left the mempool (e.g.
	// replaced by an RBF fee bump) before the block was generated.
	let stderr = String::from_utf8_lossy(&gen_out.stderr);
	assert!(stderr.contains("not in mempool"), "bitcoin-cli generateblock failed: {stderr}");
	}
	panic!("bitcoin-cli generateblock failed {MAX_ATTEMPTS} times: mempool kept changing");