Improve clarity about wallet balances in the Wallet UI

[waynecollier-da]

The current Wallet UI obscures the differences between pending holding fees, locked Amulet / Canton Coin, total holdings, and available balance.

We should communicate these various elements of users holdings more clearly.

Add a view to the Wallet UI that shows:

• Total Holdings
• Locked holdings
• Pending holding fees
• Available balance

Where the Available balance is the Total holdings less locked holdings and pending holding fees.