gui: Refresh "send coins" page design

[cyrossignol]

This tweaks the design and styles of the GUI "send" page as an adaptation of the proposed designs in #847. Most significantly, I added a header feature common to the new look and updated the coin control section. The mock ups in #847 provide no guidance for the coin control features, so I followed the "sub-header tools section" pattern present in some of the designs. The appearance differentiates the coin control settings from the recipient forms.

The proposed designs reorganize some of the buttons and fields. I chose to omit those adjustments because of usability issues for small screens and because some do not accurately represent the behavior of this form. I also did not implement any new features. We can save these for the full redesign:

• A detachable recipient form (I'm skeptical about the value of this functionality)
• A popover-type address picker widget

I will update any outstanding icons as a whole in a separate PR.

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The coin control features section now behaves as an expandable panel. Opening the panel and completing the requisite parts of the form activates coin control options for the pending transaction, and collapsing the panel disables the options. I added a status indicator to more clearly communicate when the coin control configuration applies because the tool is a bit ambiguous for unfamiliar users.

Since the coin control section is always available on the page now, I removed the checkbox that toggles the feature from the options dialog. I hate that it was buried so deeply behind a series of menus. For a proof-of-stake coin, the coin control features can be a significant part of the experience, and these features are the only user-facing privacy tools available in Gridcoin right now, so exposing them (as optional) by default provides users with a better chance to learn about the functionality. This also makes the new consolidation feature easier to find. This PR fixes some state issues in the original coin control toggle.

[cyrossignol]

Rebased and fixed a small issue with the coin control change address status label leftover from #2125.

[jamescowens]

I like this new treatment very much. One thought provoking corner-case:

If you run the Consolidate Wizard and set up a transaction...

and then deactivate the coin control...

and reactivate it

the amount is still filled out at the bottom, but the input state has apparently been lost.

I am not sure what is the best thing to do here. It is a little confusing I think to the user. The amount that corresponds to the prior selected inputs remains, but now that will come from automatically selected inputs, which doesn't make any sense.

You can clear it manually of course, or rerun the wizard or inputs button to select again.

[cyrossignol]

@jamescowens I removed the reset for the coin control panel toggle. At first, I liked the way it behaved. But, on second thought, you're right—it does seem confusing.

I don't think it makes sense to fiddle with the values on the recipient forms when the coin control panel opens and closes. Can't think of any good way for that to work in those cases. We could clear it all, but that may be more frustrating to the user.

[jamescowens]

Yeah. I think removing the reset is the right thing.... If you had it open and were doing coin control, closing the panel probably indicates hiding it by the user, not necessary destroying the state.

[jamescowens]

ACK