CLC-2400 Allow range of semesters rather than all-or-one

https://jira.media.berkeley.edu/jira/browse/CLC-2400

The goal is to let us extend the range of our queries gradually, especially while the Dashboard what's-current widgets stay dependent on the everything-available-in-My-Academics data.

Started from @yuhunglin's https://github.com/ets-berkeley-edu/calcentral/pull/1505 but changed to maintain existing everything-in-the-DB tests.