Smarter selection of addresses in add-address that ensures discoverability

[danimoh]

Currently, when a user adds new addresses that span more than the ACCOUNT_MAX_ALLOWED_ADDRESS_GAP (see WalletInfoCollector) without using them, following addresses will not be detected on login even if they were used. Although obviously no funds are lost, this is confusing to the user and not user friendly.

To avoid this issue, we should only offer addresses at most 20 apart from the last created address that was actually used instead of addresses within a gap of 20 from the last created address.
A drawback of this is that the order of displayed addresses will not necessarily be the creation order anymore if the user creates a higher index first without using it then creating an additional address with lower index.