Summary:
Give UpdateThreadsTask a description method for strings like "Marked as read"
Give ChangeLabelsTask a better description method that returns shorter strings and is specific when possible
Give ChangeFolderTask a more specific description and don't assume folderOrId will always be a folder
Make it so that passive "mark as read" from the message store isn't undoable
Give the base class a description method that names the object
Change UndoRedo component CSS a bit:
- Use "inline-flexbox" with a max-width so that we can define shrinking rules on the label and Undo button (label gets ellipsis, button does not shrink at all)
- Avoid left:39%, since it assumed that the undo-redo element would be 22% of the width of the thread list, which wasn't always true. Instead, make the `undo-redo-manager` container "text-align:center", so the `undo-redo` div is always centered within it.
- Add `cursor:default` so that the user sees the pointer, not the text insertion cursor when hovering over "Undo"
- Add overflow / text-overflow so that if the message is ever too long, the user sees `...` ellipsis properly.
Test Plan: Run a few new tests
Reviewers: evan, ethanb
Reviewed By: ethanb
Differential Revision: https://phab.nylas.com/D1830
