Replace asynctask uploader with viewmodel

[grzesiek2010]

Closes #6827

Why is this the best possible solution? Were any other approaches considered?

The issue itself was not significant and could be fixed without major changes. However, it was based on a long-deprecated AsyncTask, so it was a good opportunity to replace it with modern architecture components, which I did while also ensuring the issue was properly addressed.

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

We need to carefully test the entire process of manually uploading finalized forms (from the list of forms to send), as this functionality has been refactored.

Do we need any specific form for testing your changes? If so, please attach one.

No.

Does this change require updates to documentation? If so, please file an issue here and include the link below.

No.

Before submitting this PR, please make sure you have:

• added or modified tests for any new or changed behavior
• run ./gradlew connectedAndroidTest (or ./gradlew testLab) and confirmed all checks still pass
• added a comment above any new strings describing it for translators
• added any new strings with date formatting to DateFormatsTest
• verified that any code or assets from external sources are properly credited in comments and/or in the about file.
• verified that any new UI elements use theme colors. UI Components Style guidelines