Layer re-ordering

[jauyong]

Feature description

Controls that allows moving blocks backwards and forwards (e.g. behind another block or bring on top of another block). Implemented in sidebar and dedicated layer panel.

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Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry

[samitron7]

Here are the behaviors for re-ordering in the layers panel. Note that the re-ordering behavior should be consistent with that for re-ordering thumbnails in the carousel and the grid view (ie we like for it to be all consistent).

Anatomy of Layers Panel:
https://www.figma.com/file/Cd9iacVknHK62RO4pRwb68/Stories-Editor?node-id=2683%3A260

Re-ordering behavior:

1. Drag and drop
2. Cut/paste to re-order
   https://www.figma.com/file/Cd9iacVknHK62RO4pRwb68/Stories-Editor?node-id=2715%3A1632

[barklund]

Only panel refactor has been completed - still needs actual layer panel.

[pbakaus]

@barklund this seems done except for the keyboard shortcuts, right?

[barklund]

@barklund this seems done except for the keyboard shortcuts, right?

Yes, and keyboard shortcuts were actually added in #320, also merged.