[Cashtab] Add ability to rename active wallet

Summary: Related to task T2132. Added logic to renameWallet in useWallet.js that checks if the wallet to be renamed is the currently active wallet, sets newWalletName for the currently active wallet. I did not include the delete wallet button for the currently active wallet, but this can be added if it is desired.

Test Plan:
cd web/cashtab && npm start
navigate to the Configure screen
note that the saved wallets collapse is present even if there is only one saved wallet
Note that the currently active wallet now shows the add to address button & the edit name button
Edit the name of the currently active wallet
Observe that the active wallet's name has changed

From the wallet label component in Send, Airdrop, or Home screen, click the edit button,
Observe that the browser is routed to the Configure screen with the RenameWalletModal open,
Change the wallet name,
Observe that the wallet's name changes in the SW in local storage, the SW list on the configure screen, and in the wallet label component.

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D11823