assumeutxo: Ensure transactions are not presented as confirmed until background sync is complete

[luke-jr]

AFAIK currently if assumeutxo were to be used, transactions might get shown as confirmed even while the entire chainstate is unconfirmed. This should be fixed before releasing with assumeutxo enabled for mainnet.

[Sjors]

I can see the utility of showing transactions as unconfirmed in the GUI. The alternative would be to present the assumed state some other way, which might be confusing.

But if we do that, we need to add an exception to our policy of not spending unconfirmed received. Depending on the GUI status is implemented, I suspect this will just work, because coin selection ignores assume-utxo stuff.

[pablomartin4btc]

Only in the GUI? What about rpc command listtransactions?

[Sjors]

@pablomartin4btc I also added that in #28616