When adding reviewers in pull requests, always sort team members to the top (BB-9439)

Repro:

Create a new pull request in a team repo, and start typing a few characters into the reviewers box to autocomplete a team member's name.

Expected: If a team member matches, that person is always sorted above non-team members.

Actual: if a bitbucket user id from someone outside the team matches exactly, that user ID is sorted to the top, resulting in accidental adds of people outside our org.

Example:

If I type in only 'd', 'James DeMichele' is matched and sorted at the top, but if I get to "dem" (which happens frequently because I'm a fast typist) then the bitbucket user '@ dem' is matched and sorted above 'James DeMichele', and pressing enter tries to add that person instead.