Tx-Sync: Track spent WatchedOutputs and re-add if unconfirmed

[tnull]

Fixes #2734.

• Previously, we would track a spending transaction but wouldn't account for it being reorged out of the chain, in which case we wouldn't monitor the WatchedOutputs until they'd be reloaded on restart.
  In the first commit, we keep any WatchedOutputs around until their spends are sufficiently confirmed and only prune them after ANTI_REORG_DELAY.

• Moreover, we dedup any ConfirmedTxs entries before handing them to Confirm::transactions_confirmed. Previously, we would just push to the confirmed_txs Vec, leading to redundant Confirm::transactions_confirmed calls, especially now that we re-confirm previously disconnected spends.
  In the second commit, we ensure that we don't push additional ConfirmedTx entries if already one with matching Txid is present. This not only gets rid of the spurious transactions_confirmed calls (which are harmless), but
  more importantly saves us from issuing unnecessary network calls, which improves latency.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.01%. Comparing base (2c9dbb9) to head (b71c6e2).
Report is 27 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2946      +/-   ##
==========================================
+ Coverage   89.18%   90.01%   +0.83%     
==========================================
  Files         117      117              
  Lines       95541    99416    +3875     
  Branches    95541    99416    +3875     
==========================================
+ Hits        85205    89489    +4284     
+ Misses       7840     7714     -126     
+ Partials     2496     2213     -283     

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[TheBlueMatt]

One nit, otherwise LGTM.

[jkczyz]

Looks good modulo the comments.

[jkczyz]

LGTM. Feel free to squash.

[jkczyz]

nit: may as well pass txid by value

[tnull]

Done.

[tnull]

Squashed commits and included the following changes:

> git diff-tree -U2 d7dafc94 b71c6e2f6
diff --git a/lightning-transaction-sync/src/esplora.rs b/lightning-transaction-sync/src/esplora.rs
index e7952d6c2..538918ada 100644
--- a/lightning-transaction-sync/src/esplora.rs
+++ b/lightning-transaction-sync/src/esplora.rs
@@ -274,5 +274,5 @@ where
                                continue;
                        }
-                       if let Some(confirmed_tx) = maybe_await!(self.get_confirmed_tx(&txid, None, None))? {
+                       if let Some(confirmed_tx) = maybe_await!(self.get_confirmed_tx(*txid, None, None))? {
                                confirmed_txs.push(confirmed_tx);
                        }
@@ -297,5 +297,5 @@ where
                                                if let Some(confirmed_tx) = maybe_await!(self
                                                        .get_confirmed_tx(
-                                                               &spending_txid,
+                                                               spending_txid,
                                                                spending_tx_status.block_hash,
                                                                spending_tx_status.block_height,
@@ -320,5 +320,5 @@ where
        #[maybe_async]
        fn get_confirmed_tx(
-               &self, txid: &Txid, expected_block_hash: Option<BlockHash>, known_block_height: Option<u32>,
+               &self, txid: Txid, expected_block_hash: Option<BlockHash>, known_block_height: Option<u32>,
        ) -> Result<Option<ConfirmedTx>, InternalError> {
                if let Some(merkle_block) = maybe_await!(self.client.get_merkle_block(&txid))? {
@@ -335,5 +335,5 @@ where
                        let mut indexes = Vec::new();
                        let _ = merkle_block.txn.extract_matches(&mut matches, &mut indexes);
-                       if indexes.len() != 1 || matches.len() != 1 || matches[0] != *txid {
+                       if indexes.len() != 1 || matches.len() != 1 || matches[0] != txid {
                                log_error!(self.logger, "Retrieved Merkle block for txid {} doesn't match expectations. This should not happen. Please verify server integrity.", txid);
                                return Err(InternalError::Failed);
@@ -343,5 +343,5 @@ where
                        let pos = *indexes.first().unwrap() as usize;
                        if let Some(tx) = maybe_await!(self.client.get_tx(&txid))? {
-                               if tx.txid() != *txid {
+                               if tx.txid() != txid {
                                        log_error!(self.logger, "Retrieved transaction for txid {} doesn't match expectations. This should not happen. Please verify server integrity.", txid);
                                        return Err(InternalError::Failed);
@@ -350,10 +350,10 @@ where
                                if let Some(block_height) = known_block_height {
                                        // We can take a shortcut here if a previous call already gave us the height.
-                                       return Ok(Some(ConfirmedTx { tx, txid: *txid, block_header, pos, block_height }));
+                                       return Ok(Some(ConfirmedTx { tx, txid, block_header, pos, block_height }));
                                }

                                let block_status = maybe_await!(self.client.get_block_status(&block_hash))?;
                                if let Some(block_height) = block_status.height {
-                                       return Ok(Some(ConfirmedTx { tx, txid: *txid, block_header, pos, block_height }));
+                                       return Ok(Some(ConfirmedTx { tx, txid, block_header, pos, block_height }));
                                } else {
                                        // If any previously-confirmed block suddenly is no longer confirmed, we found