Add Testnet balances to 'Testnet' wallets mode

Switch networks to testnet, and see that now the 'Wallets' page shows all wallets blank.

Show a horizontal list of testnet balances like this:

|chain icon|: 0.01 |chain icon|: 1.54 |chain icon|: 12.32

For any non-zero testnet balances on each wallet. Only show the first 3 balances you find, this should be sufficient for users to find their wallets with testnets.

The chain icon should not be fullsize, should look smaller than the icons in the main wallet page, maybe use the same size as the UserAvatar on the main wallet page.