This adds detail to the balance command of the CLI wallet to show how
much has been batched for each address and also summarises when the next
payout is.

It also includes additional fields to get_balance rpc endpoint on the
oxen-wallet-rpc so the user can check on the status of their accrued
funds.

If omitted it looks up the current wallet primary address (which is
usually what we want).

wallet2_api needs to provide a way to to get at this.

Also changed the existing wallet_rpc_server and simplewallet code to use
the new wallet2 method.

This cuts the size of the response by about 75%.

Unlike a vector, if a std::array doesn't exist in the response epee
chokes.  This fixes it to make it silently ignore it (and leave the
array values untouched), which just makes it consistent with what it
does for any other type of field.

This is particularly needed to be able to retrieve service_node_info
with the `service_node_version`, `lokinet_version`, and
`storage_server_version` fields omitted without getting a
deserialization failure from the omission.

E.g.:

    [wallet T6TSSZ (has locked stakes)]: balance
    Currently selected account: [0] Primary account
    Tag: (No tag assigned)
    Balance: 73541.719401728, unlocked balance: 72339.332202963 (23 block(s) to unlock)
    Total staked: 919.987654321, 0.000000000 unlocking
    Pending SN rewards: 49.419920278,  (next payout: block 10433, in about 26 minutes)