Define structs that will be used for backup options and add some CLI
helpers/tests to populate those structs with flag values
Rate limiter config is pulled out as a separate struct because it will
likely be used for backup and restore operations and it has values that
are [passed separately](505c06441a/src/internal/m365/backup.go (L232)) to the rate limiter config code
---
#### 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
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup
#### Test Plan
- [ ] 💪 Manual
- [x] ⚡ Unit test
- [ ] 💚 E2E