[electrum] pass a wallet.contacts reference to ContactList

Summary:
Remove some coupling between ContactList and ElectrumWindow.
There is no change in behavior.

Depends on D14534

Test Plan: repeat test plan from D14534

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D14535