RFC: Refactor Enrollment & Grade Distribution Popovers to Modals

[KevinWu098]

Having these large charts render on hover feels incorrect -- when moving across search results, these popovers often appear when unwanted (simply because the mouse ends up moving over it on scroll)

Moving to use modals, on click, would allow for larger charts, and possibly more detail (especially on mobile)

IIRC, the original intent for onHover was for ease of access, but I believe users would prefer an explicit opt-in (i.r. clicking)

[KevinWu098]

Closed by #1137