[Tagging] Add "Expand All" button to Taxonomy View

[bradenmacdonald]

1. When viewing or editing a taxonomy with hierarchical tags, the new "Expand All" button should load and display all children/grandchildren of the currently visible page of root tags.
2. If all the children/grandchildren are visible, the button should change to "Collapse all"
3. If the Taxonomy has more than TBD: X tags, the "Expand all" functionality can be disabled, as it would require loading too much data.

[pomegranited]

This functionality has already been added to the tags list using DataTable's expandable rows feature.

So this ticket about moving that "expand all" button into the table header, as per the designs, which might require changes to paragon. CC @bradenmacdonald

[bradenmacdonald]

@ali-hugo do you think we can just leave this as-is for MVP? I know the Figma are more wireframes than finalized UX, so I'm thinking if the "Expand All" is basically present and working, it's not worth spending much time on this now until after we've had a round of user testing and feedback.

So @pomegranited I'm thinking let's just call this done for now, but wait to see what Ali says.

We can put any follow-ups into https://github.com/openedx/modular-learning/issues/155 which is probably a better idea anyways since we'll have to make sure we account for things like dragging tags around, multi-select of tags, keyword filtering, etc. I think we can still do all of that using this same as a basis but things could change.

Here's how it looks now:

[pomegranited]

FYI @ChrisChV ^

[ali-hugo]

@ali-hugo do you think we can just leave this as-is for MVP?

@bradenmacdonald @pomegranited @chrischv Yes, I think this is ok to leave as is for MVP. The only thing I think might be worth tweaking (but only if it's a quick change), would be to lose the "child tags" column, and rather include a little gray number next to the parent tags (just like the child tags have). But if that's not a simple fix, I think @bradenmacdonald's right when he says we should leave this as is until we have some user feedback. 👍

[bradenmacdonald]

@ali-hugo Yep that should be a simple change, and we can include that in https://github.com/openedx/modular-learning/issues/157 . CC @pomegranited. BTW I realized that we're only showing the number of "child" tags, not the total number of "child+grandchild+etc." tags, which doesn't match the designs. I think we'll probably need to change that at some point, but that's not as simple a change.