Allow import of the wallet from the transaction

When unknown wallet is used in a transaction but cosigners are known we can offer the user to create the wallet.
This will make UX much better.

Start by tracing the transaction-handling entry point and the existing wallet creation or import flow to understand how unknown wallets and known cosigners are represented. Done means the user is offered a way to create the wallet when the transaction references an unknown wallet but its cosigners are known; the issue does not name specific files or tests.

Written by the indexing model from the issue text.