Fix bug where we tried to create folders with an empty display name
when the user did a restore with `/` or `""` as the restore destination
for contacts
This PR is safe with the current flow for backing up contact folders
because nested folders aren't backed up at all (at least nesting beyond
the first level). It is unclear, though possible, that this patch will
continue to work if we backup nested contact folders
Also adds basic smoke tests for this issue for all exchange data types
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#### Does this PR need a docs update or release note?
- [x] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [ ] ⛔ No
#### Type of change
- [ ] 🌻 Feature
- [x] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup
#### Test Plan
- [x] 💪 Manual
- [x] ⚡ Unit test
- [ ] 💚 E2E
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