test(StopDetailsViewModel): Address remaining flakiness

[KaylaBrady]

Summary

Follow up to #675, which introduced some tests that are still flaky.

What is this PR for?

An attempt to resolve flakiness in the stopDetailsManagedVM tests. I expaned the use of the StandardTestDispatcher recommended here to the view model in each managedVM test. These tests passed running repeatedly locally, except for testManagerHandlesTripFilterChange which consistently failed until I also added composeTestRule.awaitIdle() I'm not entirely sure why that test in particular was failing.

If these continue to flake after these changes, then we should take @EmmaSimon's suggestion of skipping them for now and make a ticket to follow up on them.

iOS

• If you added any user-facing strings on iOS, are they included in Localizable.xcstrings?
  • Add temporary machine translations, marked "Needs Review"

android

• All user-facing strings added to strings resource
• Expensive calculations are run in withContext(Dispatchers.Default) where possible

Testing

What testing have you done?