Give activity titles even more space [#60007192]

Also, catches RITES up with theme changes made for Interactions.

https://www.pivotaltracker.com/story/show/60007192
Allow introduction to use full width [#59367158]

https://www.pivotaltracker.com/story/show/59367158
Reduce vertical spacing between embeddables in HAS

This also incorporates a bunch of vertical-space-compression steps taken for Interactions and RITES. First iteration; we may see some further iteration. [#59366098]

https://www.pivotaltracker.com/story/show/59366098
Deal with alignment of sequence titles in themes.

[#59364378] This was originally done in Interactions, now it's in HAS and RITES as well.

https://www.pivotaltracker.com/story/show/59364378