Merge bitcoindevkit/bdk#1279: Filter duplicate coins before coin selection

5299db34cb fix(wallet): filter duplicates before coin selection (志宇)
d9501187ef test(wallet): fix tests helpers to generate unique utxos (志宇)

Pull request description:

  Fixes #1240

  ### Description

  We now filter out duplicate coins before calling `CoinSelectionAlgorithm::coin_select`. If a UTXO exists in both `required_utxos` and `optional_utxos`, only the copy in `required_utxos` will be kept.

  Test helper methods are also updated to not create duplicate UTXOs.

  ### Changelog notice

  Fixed

  * Filter out duplicate UTXOs before calling `CoinSelectionAlgorithm::coin_select`. If a UTXO exists in both `required_utxos` and `optional_utxos`, only the copy in `required_utxos` will be kept.

  ### 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

  #### Bugfixes:

  ~* [ ] This pull request breaks the existing API~
  * [x] I've added tests to reproduce the issue which are now passing
  * [x] I'm linking the issue being fixed by this PR

ACKs for top commit:
  danielabrozzoni:
    utACK 5299db34cb

Tree-SHA512: 9cb5517b7f74f89c06172efc344766b16b3216a25b1ebdd6eb84767a9e103124cead9eb0a7f3b5feb562fbb925517a9bf0404399de74b4e898982a5b3795aa04

crates/bdk/src/wallet/mod.rs

@@ -1546,6 +1546,9 @@ impl<D> Wallet<D> {
             }
         };
 
+        let (required_utxos, optional_utxos) =
+            coin_selection::filter_duplicates(required_utxos, optional_utxos);
+
         let coin_selection = coin_selection.coin_select(
             required_utxos,
             optional_utxos,