Returning promise in $.wikibase.listview.enterNewItem()

Improves code structure and removes need to register event listeners in most cases.

Change-Id: Ic99a1f44d991f4d8881b11686fed523ffcda0435
(cherry picked from commit f42d837891af135c5ba2466a92b2b5b645a4a451)
Focus snakview when adding a new snakview to a referenceview

Bug: T76860
Change-Id: I880efbb0f6e133ffa4dac36124fb1a3d522329fe
(cherry picked from commit 8ce05b93fd4f32d9efe3cce5af42d94545c4d27e)
Focus new snakview when adding a qualifier

Bug: T76860
Change-Id: I736ae0614579b566619cbf89e3b5e48c03dfd97e
(cherry picked from commit cc631d661e52004f56c40e213644b05a3e29f634)
Merge "Focus new snakview when adding a qualifier" into wmf/1.25wmf12
Merge "Focus snakview when adding a new snakview to a referenceview" into wmf/1.25wmf12
Merge "Returning promise in $.wikibase.listview.enterNewItem()" into wmf/1.25wmf12