Perf: speed up accountUserCourseSearch page load
Perf: speed up accountUserCourseSearch page load

closes: COREFE-384

Instead of getting all these timezone files at page load, we just get
The one that the user needs as a separate request

Before: https://cl.ly/6286bad48ccb
After: https://cl.ly/6b72d7d52f4c

Test plan:
* in non-english:
* go to /accounts/x/users
* click the “pencil” icon on a row to edit a user
* the select box to edit their timezone should work the same as it did
  before

Change-Id: Ie4e5ca5c81131b31279ee101760796781b0eaaa9
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/214711
Tested-by: Jenkins
Reviewed-by: Clay Diffrient <9dff2e5c98626d20d2848250c411e8009465bb87@instructure.com>
QA-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms