[Tagging] Access unit/component tags from the Unit page

[bradenmacdonald]

"As a content author, I can see what tags have been applied to a unit in my course (from within the unit page)"

"As a content author, I can see what tags have been applied to individual components in my course (from the unit page)"

Follows #118

Acceptance criteria

1. In the right sidebar on the unit page, it indicates how many tags the unit has, shows the specific tags (collapsed at first), and has a button to open the tag drawer (same tag drawer as from [Tagging] Display a unit's tags in the tag drawer #118).
   
   

2. For each individual component (XBlock), the "three dots" menu gets a new "Manage tags" option which will open the tag drawer for that component.
   

Developer notes

• Screenshots above are for convenience - Figma is the most up-to-date source for mockups. The scale of UI elements seen in the screenshots above may be incorrect.

[ali-hugo]

@ChrisChV @bradenmacdonald Thanks for your work on this! It's looking good. Here are a few small things I noticed when clicking through the sandbox:

• There is a strange 'jump' when I first expand the "Tags" sidebar component. The area containing the "Tags" heading, tag count, and up/down arrow seems to shift down a few pixels when it is first clicked
• This section also shows a dotted outline after it is selected (see screenshot below):

• If a tag cannot be expanded (i.e. leaf tags), it should not have a hover state (in the screenshot below, "flat taxonomy tag 2949" should be black, not blue):

Please change the order of the items in the component menu to:

• Manage Access
• Move
• Manage tags
• Copy to Clipboard
• Duplicate
• Delete

[bradenmacdonald]

^ We will fix the above shortly in #157