handle / improve txo spend scenario / timeout with large wallets

[tzarebczan]

Users with large amounts of UTXOs time out when trying to do txo spend to consolidate their wallet. The same would happen for txo spend on unlocking all tips (coming to the app soon).

I think part of the problem is the large DBs (#2876) and selecting the UTXOs, and the other is just the sheer amount of them to create the multiple transactions needed.

I can also try with the sqlite coinchooser if that's better, but we haven't been using it due to some issues (#3004).

If we had a way to increase the client side timeout for certain calls, that would help at least get the transactions through.