Refactor syncUpload Method to improve flow and error handling

[omarismail94]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

One of the PRs to fix #760

Description
Clear and concise code change description.

• syncUpload method is now structured to emit Flow<FetchProgress>
• eliminated Flow<UploadState> and instead, have the uploader return an UploadSyncResult, that can be processed by the syncUpload method
• Improved readability, with a clear and understandable flow of logic. Each step of the process is now more coherent and aligned with its functionality, improving maintainability (no more returning a flow within a flow and making sure you collect both at different places in the code)

Current upload:

Proposed upload:

Alternative(s) considered
Have you considered any alternatives? And if so, why have you chosen the approach in this PR?

Type
Choose one: (Bug fix | Feature | Documentation | Testing | Code health | Builds | Releases | Other)

Screenshots (if applicable)

Checklist

• I have read and acknowledged the Code of conduct.
• I have read the Contributing page.
• I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA.
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project.
• I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally.
• I have built and run the demo app(s) to verify my change fixes the issue and/or does not break the demo app(s).

[jingtang10]

have you tested the demo app with this?

[omarismail94]

have you tested the demo app with this?

@jingtang10 yes, and it worked. I was able to see the upload status update emissions being printed in the logs

[jingtang10]

woohoo!