Rename `OutputStatus` to `OutSpendStatus`

[evanlinjin]

OutputStatus is the wrong name. It is really the status of the output's spend.

[tnull]

Not sure? It has a spent: bool field, so it's really describing the status of the output itself? What would be missing to make it a real OutputStatus?

However, if someone touches it already, the status field probably should be renamed too, as it would be less confusing to name it spending_tx_status, tx_status or similar.

[MaxFangX]

The Esplora API docs describes the endpoint as "Returns the spending status of a transaction output." I noticed the difference in names when touching this area, but like BDK's current name of OutputStatus which I think is more accurate. Furthermore, I think the difference between outspend and output is small enough that people won't have trouble recognizing it if they end up reading the Esplora api docs.