Fix upload status cache issue

[malinajirka]

Fixes #11303

A single instance of PostModelUploadStatusTracker is injected into PagesViewModel and reused in all the child view models. This fixes the issue as all the vms are working with the same instance and the cache is always up to date.

To test:

1. Smoke Test: Try to publish a post and make sure the progress bar indicator is shown

I tested it by merging this branch into #11266 and:

1. Open Page list
2. Turn on airplane mode
3. Open a page and make changes
4. Click on Update/Publish
5. Find the page in the page list
6. Click on the "Cancel" action
7. Make sure the Cancel action disappears

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can test the changes on this Pull Request by downloading the APK here.

[jd-alexander]

Thanks for these changes Jirka! Tested and it works as expected! LGTM 🚢