## Description
General cleanup/consolidation of code for getting OneDrive collections during backup. Few minor changes to behavior:
* always return a collection for the root folder even if it's empty
* add items to the exclude list only after they've been added to a collection. This gives a better chance of preserving the item even if we encounter an error parsing paths or something. If there's a failure, the old version of the item is most likely to be preserved (this varies based on whether the item is returned in multiple delta results during the backup)
## Does this PR need a docs update or release note?
- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No
## Type of change
- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Test
- [ ] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup
## Issue(s)
* #2447
## Test Plan
- [ ] 💪 Manual
- [x] ⚡ Unit test
- [ ] 💚 E2E
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