## Description
Add functions to Collection and Stream interfaces that allow for getting
more information about the difference between the previous backup and
the currently in-progress one. These will allow delta token-based
incremental backups to determine how the state has evolved.
Current code does not use these functions and return values for them
are "default" values that should result in full backups even if
KopiaWrapper is updated to start checking the values and GraphConnector
still pulls all items
These functions are not used during restore and can return "default"
values
## Type of change
<!--- Please check the type of change your PR introduces: --->
- [x] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Test
- [ ] 💻 CI/Deployment
- [ ] 🐹 Trivial/Minor
## Issue(s)
* #1700
## Test Plan
<!-- How will this be tested prior to merging.-->
- [ ] 💪 Manual
- [x] ⚡ Unit test
- [ ] 💚 E2E
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