Formerly, actions were handling the UI logic for closing and deleting

review requests, and unified banner was handling all discard logic.

There was some overlap in that both were implementing review request

discard logic. And then some of that logic ended up running two

instances of the same navigateTo().
Some of those actions provided confirmation of operations using the old

modalBox, which is a couple generations out of date.
This change reworks all of this to better centralize logic and update

the UI.
ReviewRequestEditorView now has new methods that handle some of this

common logic:

closeCompleted()
closeDiscarded()
deleteReviewRequest().
discardDraft()

The actions can call this directly, and no longer need to reimplement

any of the logic. This simplifies them considerably.
UnifiedBannerView also calls out to two of these: closeDiscarded()

and discardDraft(). It no longer has its own confirmation dialog logic

for these.
All operations requiring confirmation now use Ink's new

showConfirmDialog(), and use reworked confirm button labels that

better convey the action being invoked. These new versions keep the

dialog open while the operation is being performed, managing the busy

state on the confirm button.
The post-operation page refreshes/navigation no longer live in any of

these functions. We had code already that handled this as a result of

various signals, and were just missing one for deleting review requests,

which have been added. We also no longer need the closeError signal,

handling error handling instead in the central functions.
There's also a fix for error reporting for closing review requests. When

closing was converted to actions, the triggering of closeError was

performed on the wrong object, meaning we weren't handling it correctly.

This is no longer a problem with the new implementation.

Unit tests pass.
Tested each of the actions and buttons on the Close menu and Unified

Banner, both canceling and performing the action. Checked the message

handling as well.