Merge bitcoindevkit/bdk#1441: Remove duplicated InsufficientFunds error member

Merge bitcoindevkit/bdk#1441: Remove duplicated InsufficientFunds error member

29c8a00b435bdf2fa1d7c707ad09c1a47edc07b3 chore(wallet): remove duplicated InsufficientFunds error member from CreateTxError (e1a0a0ea)

Pull request description:

  closes #1440

  ### Description

  - Replace `CreateTxError::InsufficientFunds` use by `coin_selection::Error::InsufficientFunds`
  - Remove `InsufficientFunds` member from `CreateTxError` enum
  - Rename `coin_selection::Error` to `coin_selection::CoinSelectionError`

  ### Notes to the reviewers

  - We could also keep both members but rename one of them to avoid confusion

  ### 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 29c8a00b435bdf2fa1d7c707ad09c1a47edc07b3
  notmandatory:
    ACK 29c8a00b435bdf2fa1d7c707ad09c1a47edc07b3

Tree-SHA512: a1132d09929f99f0a5e82d3ccfaa85695ae50d7d4d5d9e8fd9ef847313918ed8c7a01005f45483fef6aeae36730a0da2fed9a9f10c3ce2f0a679527caf798bfe