Improve labels on post list items when a post is pending upload

[malinajirka]

When the user clicks on "publish/schedule/submit" when offline, the post is added to the upload queue.

The goal of this task is to add labels to the post list items and update Snackbar messages as per design in #9555.

Note: This issue depends on and should be released along with #10177.

[malinajirka]

I've started working on this issue in issue/10207-pending-upload-labels.

However, I'm waiting on a reply to this comment.

[malinajirka]

The up-to-date design and behavior definition for Snackbar and label can be found in wordpress-mobile/WordPress-iOS#12227