Improve wallet recovery algorithm

[mrose17]

Test Plan

1. about:preferences#payments, 'Advanced Settings..., 'Backup your Wallet', ' Save recovery file...', save as brave_wallet_recovery.txt`
2. get a vanilla browser install and turn on the ledger -- this creates a new wallet (with a new wallet address)
3. about:preferences#payments, 'Advanced Settings..., 'Recovery your Wallet', ' Import recovery keys', select brave_wallet_recovery.txt`
4. verify that value of properties.wallet.address does not change after step 3

Description

Fixes #7288

[bsclifton]

Tried it out; worked as expected. LGTM 😄