lightningd: help memleak scan into replay_tx hash table to avoid false positives.

```
**BROKEN** lightningd: MEMLEAK: 0x5557327d1428
**BROKEN** lightningd:   label=lightningd/onchain_control.c:352:struct replay_tx
**BROKEN** lightningd:   alloc:
**BROKEN** lightningd:     /home/runner/work/lightning/lightning/ccan/ccan/tal/tal.c:488 (tal_alloc_)
**BROKEN** lightningd:     /home/runner/work/lightning/lightning/lightningd/onchain_control.c:352 (replay_watch_tx)
**BROKEN** lightningd:     /home/runner/work/lightning/lightning/lightningd/onchain_control.c:1816 (onchaind_funding_spent)
**BROKEN** lightningd:     /home/runner/work/lightning/lightning/lightningd/onchain_control.c:1860 (onchaind_replay_channels)
**BROKEN** lightningd:     /home/runner/work/lightning/lightning/lightningd/lightningd.c:1407 (main)
**BROKEN** lightningd:   parents:
**BROKEN** lightningd:     lightningd/onchain_control.c:1856:struct replay_tx_hash
**BROKEN** lightningd:     lightningd/lightningd.c:112:struct lightningd
```

Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell

lightningd/onchain_control.c

@@ -5,6 +5,7 @@
 #include <ccan/tal/str/str.h>
 #include <common/htlc_tx.h>
 #include <common/key_derive.h>
+#include <common/memleak.h>
 #include <common/psbt_keypath.h>
 #include <db/exec.h>
 #include <errno.h>
@@ -47,6 +48,13 @@ static bool replay_tx_eq_txid(const struct replay_tx *rtx,
 HTABLE_DEFINE_TYPE(struct replay_tx, replay_tx_keyof, txid_hash, replay_tx_eq_txid,
 		   replay_tx_hash);
 
+/* Helper for memleak detection */
+static void memleak_replay_tx_hash(struct htable *memtable,
+				   struct replay_tx_hash *replay_tx_hash)
+{
+	memleak_scan_htable(memtable, &replay_tx_hash->raw);
+}
+
 /* We dump all the known preimages when onchaind starts up. */
 static void onchaind_tell_fulfill(struct channel *channel)
 {
@@ -1856,6 +1864,8 @@ void onchaind_replay_channels(struct lightningd *ld)
 			channel->onchaind_replay_watches = tal(channel, struct replay_tx_hash);
 			channel->onchaind_replay_height = blockheight;
 			replay_tx_hash_init(channel->onchaind_replay_watches);
+			memleak_add_helper(channel->onchaind_replay_watches,
+					   memleak_replay_tx_hash);
 
 			onchaind_funding_spent(channel, tx, blockheight);
 			onchaind_replay(channel);