Move backend transform functions to utils module

[maxx1128]

Issue Description

For the transform files in modules/debts_api/lib/debts_api/v0/fsr_form_transform, methods that are class-agnostic should be moved to modules/debts_api/lib/debts_api/v0/fsr_form_transform/utils.rb. These are functional components that have no class-specific intent or function.

Back end tasks

• [x] Move sum_values from modules/debts_api/lib/debts_api/v0/fsr_form_transform/asset_calculator.rb.
• [x] Move safe_number and safe_sum modules/debts_api/lib/debts_api/v0/fsr_form_transform/enhanced_expense_calculator.rb.
• [x] Check other classes in this director for other functions to migrate.

Acceptance Criteria

• [ ] All specs still pass after the needed refactors

Appendix

Product notes

Tech notes

---

How to configure this issue

• [ ] Attached to a Milestone (when will this be completed?)
• [ ] Attached to an Epic (what body of work is this a part of?)
• [ ] Labeled with Team (product support, analytics-insights, operations, service-design, Console-Services, tools-fe)
• [ ] Labeled with Practice Area (backend, frontend, devops, design, research, product, ia, qa, analytics, contact center, research, accessibility, content)
• [ ] Labeled with Type (bug, request, discovery, documentation, etc.)

[maxx1128]

As of the end of Sprint 129, this ticket's pull request is approved and ready to merge. However, we're concerned that merging it will negatively affect testing. So, we're holding off on the final merge for now.