[candidate_list] Multiselect for visit label, site, and cohort

[charlottesce]

Brief summary of changes

The filters for site, cohort and visit label are now multiselect

Testing instructions (if applicable)

1. Go to Candidate -> Access Profiles page
2. Check that you can select multiple visit labels, cohorts, and visits

Note

This is a CCNA override - https://github.com/aces/CCNA/pull/3922

[driusan]

This makes sense to me.. @racostas could you review/test?

[racostas]

LGTM.

There is a small typo in the description of the PR but all fine
in place of:
2. Check that you can select multiple visit labels, cohorts, and visits
Should be;
2. Check that you can select multiple visit labels, cohorts, and sites

Should this one go to 25 @driusan ?