Merge #1285: doc(wallet): improve docs for Wallet::sent_and_received

08b745e doc(wallet): improve docs for `Wallet::sent_and_received` (vmammal)

Pull request description:

  Thank you @thunderbiscuit for raising this issue. I noticed this method borrows the language from `SpkTxOutIndex::sent_and_received`, which this PR doesn't touch. I think in general it's desirable that methods in `bdk_chain` crate would refer to some of the core structures directly.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

ACKs for top commit:
  evanlinjin:
    ACK 08b745e

Tree-SHA512: 7f1285c4baa5fb56fd65baa5585bd343338de9988b941618a2b9ab628d869563f6f71ce842f936e7e1fb6a56f2f1e50fc3deaff858e830b7039888e4e496ce9a

Author: evanlinjin

crates/bdk/src/wallet/mod.rs

@@ -992,12 +992,11 @@ impl<D> Wallet<D> {
         })
     }
 
-    /// Computes total input value going from script pubkeys in the index (sent) and the total output
-    /// value going to script pubkeys in the index (received) in `tx`.
+    /// Compute the `tx`'s sent and received amounts (in satoshis).
     ///
-    /// For the `sent` to be computed correctly, the outputs being spent must have already been
-    /// scanned by the index. Calculating received just uses the [`Transaction`] outputs directly,
-    /// so it will be correct even if it has not been scanned.
+    /// This method returns a tuple `(sent, received)`. Sent is the sum of the txin amounts
+    /// that spend from previous txouts tracked by this wallet. Received is the summation
+    /// of this tx's outputs that send to script pubkeys tracked by this wallet.
     ///
     /// # Examples
     ///