Description

Per discussion in team chat today I'm removing the Wallet::cancel_tx function because it's name is misleading and the Wallet::mark_unused function can be used to accomplish the same function.

closes #326 and closes #212 and closes #41

Notes to the reviewers

This is an example of how to use mark_unused instead of cancel_tx

/// This marks as unused the change addresses used when creating a tx so they can be used in future transactions.
for txout in &tx.output {
    if let Some((keychain, index)) = txout_index.index_of_spk(txout.script_pubkey.clone()) {
        // NOTE: unmark_used will **not** make something unused if it has actually been used
        // by a tx in the tracker. It only removes the superficial marking.
        wallet.unmark_used(*keychain, *index);
    }
}

Changelog notice

• BREAKING: Remove Wallet::cancel_tx function. Use Wallet::unmark_used instead

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran just p before pushing

Bugfixes:

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