Use new fee estimation endpoint

[kyranjamie]

@fbwoolf's added this functionality to the extension wallet already.

We should use the same endpoint in the desktop wallet as well.

[markmhendrickson]

We have this issue for updating the UX in general around the three estimates returned by the API: https://github.com/hirosystems/stacks-wallet/issues/923

Let's move that one into design since it will be the most comprehensive solution here, unless you're thinking we should also quickly patch the desktop wallet somehow with this endpoint?

[kyranjamie]

Uhh, yeah it isn't a biggie to just default to using the middle fee.

But your call. Maybe we wanna couple this work with custom fee inputs etc?

[markmhendrickson]

Is the API not going to default to the middle fee on its end anyway? I have a faint recollection that was going to be the case. But if not, yea let's update on the client to use this new middle fee 👍

[fbwoolf]

The endpoint just returns all three estimates. The frontend has to decide what to default to.