Decouple form save code from async task

[shubham1g5]

Summary

Refactors Form Save code to decouple it from SaveToDisk Task into a helper class. This is required so that we can potentially call the form save logic outside a async task

Safety Assurance

• If the PR is high risk, "High Risk" label is set
• I have confidence that this PR will not introduce a regression for the reasons below
• Do we need to enhance manual QA test coverage ? If yes, "QA Note" label is set correctly

Automated test coverage

We have an automated integration test on form submissions.

Safety story

• It's a relatively straightforward code movement from SaveToDiskTask to FormSaveHelper without any changes in business logic.
• Tested a form submission locally