Improve moderation behaviors: show alert/inform sources and improve UX around threads (#3677)
* Dont show account or profile alerts and informs on posts
* Sort threads to put blurred items at bottom
* Group blurred replies under a single 'show hidden replies' control
* Distinguish between muted and hidden replies in the thread view
* Fix types
* Modify the label alerts with some minor aesthetic updates and to show the source of a label
* Tune when an account-level alert is shown on a post
* Revert: show account-level alerts on posts again
* Rm unused import
* Fix to showing hidden replies when viewing a blurred item
* Go ahead and uncover replies when 'show hidden posts' is clicked
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Co-authored-by: dan <dan.abramov@gmail.com>
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