Possible async bugs in MultiRangeInlineEditor tests

[njx]

I ran into an intermittent failure in MultiRangeInlineEditor-test. Looking at the code, it seems like there are two potential issues:

• the tests don't wait for async functions to complete
• the async functions that now depend on animations might not complete properly anyway since the animations aren't in the CSS used in the spec runner (similar issue to FindReplace tests fail when run as part of the unit test suite #5094)

It's not clear to me that either of these should cause the failure I saw, but they should get fixed anyway.

[njx]

Medium priority to me, nominating for sprint 32

[lkcampbell]

This is a milestone! Been a little while since I have seen a 100% ALL unit test pass...:+1: