Reading: Update grouping page to include computations, cut points, and click to see more

[kevinrobinson]

Who is this PR for?

K5 reading teams

What problem does this PR fix?

Builds forward on the work in #2360, enabling K5 reading teams to make use of benchmark reading data and data from other sources within A&R and instructional planning meetings.

What does this PR do?

Makes some improvements in navigation, but focuses mostly on the core grouping UX. This includes revising styling, adding in computations for reading groups, and enabling the "click to see more inline" interaction for an individual student.

One difference from previous mocks is that the "mentioned in notes" bit is cut here since it involves pushing that keyword-based search to the server to limit the notes shared across the whole team.

Note that most of this code is not generalized to all teams, grades, or reading benchmark assessments yet; the intention is still to pilot this tomorrow and then decide on the next iteration forward (either further revisions, or work towards generalizing for next pilot teams).

Screenshot (if adding a client-side feature)

Checklists

Which features or pages does this PR touch?

• Reading entry page
• Reading groups page

Does this PR use tests to help verify we can deploy these changes quickly and confidently?

• Included specs for changes
• Manual testing made more sense here

[kevinrobinson]

selfie