Annotation Tools: Load Tinymce in student_view

**Background:** This is a follow-up to PR #3831. According to @cpennington and @singingwolfboy there was a race condition with TinyMCE in the annotation tools which could be fixed by loading them via student_view from the XBlock API.

**Goal of PR: ** This PR focuses solely on that fix. It includes both changes to the modules in xmodule as well as to the test files to verify the fix.

**CMS Updates:** None.

**LMS Updates:** Changes to the way TinyMCE loads.

**Testing Notes:** Everything seems to be working in the local environment but the issue always seems to be on staging.