[Cashtab] Add a saved wallet to contact list
[Cashtab] Add a saved wallet to contact list

Summary: Ability to add a wallet in the Saved Wallets dropdown to the contact list.

Test Plan:
- npm start
- open the saved wallets dropdown and click on the Contact icon, and then the OK button in the confirmation modal and verify wallet is successfully added to contacts
- attempt to add the same saved wallet and verify duplication notification is displayed with no change to the contact list
- change the name of this same saved wallet, attempt to add it from the saved wallet dropdown again and ensure the same duplication notification is displayed
- change the name of the contact for this same saved wallet, attempt to add it from the saved wallet dropdown again and ensure the same duplication notification is displayed

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D11395

Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc