Fix updateViewGroupOffline() so that it doesn't hang

[ELeeScape]

Description

Tileset::updateViewGroupOffline() was hanging because it calls updateViewGroup() and loadTiles() in a loop without dispatching main thread tasks. This was a regression resulting from #1315.

Added main thread dispatches to updateViewGroupOffline() before every call to updateViewGroup() and loadTiles() and added a test to demonstrate the fix.

Also made the same fix for the deprecated updateView() function. There are no existing tests for updateView() so I didn't add one.

Issue number or link

Fixes #1335.

Author checklist

• I have submitted a Contributor License Agreement (only needed once).
• I have done a full self-review of my code.
• [] I have updated CHANGES.md with a short summary of my change (for user-facing changes).
• I have added or updated unit tests to ensure consistent code coverage as necessary.
• I have updated the documentation as necessary.

Testing plan

The new test subcase "updateViewGroupOffline does its own dispatching of main thread tasks so it doesn't get stuck" hangs without the fix, passes with the fix.

Reviewer checklist

Thank you for taking the time to review this PR. By approving a PR you are taking as much responsibility for these changes as the author.

As you review, please go through the checklist below:

• Review and run all parts of the test plan on this branch and verify it matches expectations.
  • If the issue is a bug please make sure you can reproduce the bug in the main branch and then checkout this branch to make sure it actually solved the issue.
• Review the code and make sure you do not have any remaining questions or concerns. You should understand the code change and the chosen approach. If you are not confident or have doubts about the code, please do not hesitate to ask questions.
  • Code should follow the C++ Style Guide
• Review the unit tests and make sure there are no missing tests or edge cases.
• Review documentation changes and updates to CHANGES.md to make sure they accurately cover the work in this PR.
• Verify that the Contributor License Agreement has been submitted, if needed.

[j9liu]

Thank you so much @ELeeScape! Can I trouble you to format the TestTilesetSelectionAlgorithm.cpp class for CI to pass? You can do this with npm by doing:

npm install
npm run format

Otherwise, these changes look great! I'm just reproducing the error locally to confirm the fix (per our reviewer checklist).

[ELeeScape]

@j9liu Formatting done.

[j9liu]

Thank you so much @ELeeScape! 🙏