Adds non-mempool wallet balance to overview

[ajtowns]

The wallet can contain transactions that are not accepted into the node's mempool (eg due to containing a too large OP_RETURN output, due to too low a feerate, or due to too many unconfirmed ancestors). In the event you end up in this situation, it can appear as if funds have gone missing from your wallet due to the non-mempool balance not being reported. Correct this by reporting the non-mempool balance.

Depends on bitcoin/bitcoin#33671

[DrahtBot]

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Conflicts

No conflicts as of last run.

[ajtowns]

To test, start with -datacarriersize=10, and run

send '{"data": "4368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73"}' null "unset" 1

from the console. "Non-mempool: " should appear in the Balances pane on the Overview window with the change from the transaction. Restarting with -datacarriersize=100000 should allow the tx to enter the mempool, and move the amount into the Available balance. (Presumably, do this on -regtest after generating 100 blocks; or perhaps signet after grabbing some funds from a faucet)

[ajtowns]

Screenshot:

The negative sign for the non-memool stuff isn't really very clear, perhaps.

[ajtowns]

Rebased after merge of parent PR, should be ready to review. Happy to close if some someone wants to take over.