<!-- PR description-->
* Integrates corso extensions into onedrive/sharepoint library item backup flows.
* Also includes integration tests for OD/SP, unit tests for collections.
* Includes a small fix for `rw *backupStreamReader Close()`
Remaining things which will be covered in later PRs:
* extension tests with incremental backups
* Observability related changes for extensions
---
#### Does this PR need a docs update or release note?
- [ ] ✅ Yes, it's included
- [x] 🕐 Yes, but in a later PR
- [ ] ⛔ No
#### Type of change
<!--- Please check the type of change your PR introduces: --->
- [x] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup
#### Issue(s)
<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* internal
#### Test Plan
<!-- How will this be tested prior to merging.-->
- [ ] 💪 Manual
- [x] ⚡ Unit test
- [x] 💚 E2E
Introduces a counting bus, and threads it into restore operations so that we can count the number of
collision skips that occur.
---
#### Does this PR need a docs update or release note?
- [x] ⛔ No
#### Type of change
- [x] 🌻 Feature
#### Issue(s)
* #3562
#### Test Plan
- [x] ⚡ Unit test
- [x] 💚 E2E
This is primarily an exercise in reducing the number of circular imports we get from adding the tester package to other packages.
No logic changes. Purely movement/renaming.
---
#### Does this PR need a docs update or release note?
- [x] ⛔ No
#### Type of change
- [x] 🤖 Supportability/Tests
#### Test Plan
- [x] ⚡ Unit test
- [x] 💚 E2E
Moves operations integration backup tests into a
subpackage, and slices up the test folder into
multiple, service specific folders.
No logic changes, only code copy-pasting and
renaming.
---
#### Does this PR need a docs update or release note?
- [x] ⛔ No
#### Type of change
- [x] 🤖 Supportability/Tests
#### Test Plan
- [x] 💚 E2E
