Add the required wiring for SDK consumers to set the min epoch duration
(and eventually other persistent config info). This is just boiler-plate
with some tests at the various layers to make sure that layer is run as
expected. More nuanced tests about setting various config values are
left to the code in `internal/kopia/conn_test.go`
---
#### 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
- [x] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup
#### Issue(s)
* #4782
#### Test Plan
- [ ] 💪 Manual
- [x] ⚡ Unit test
- [ ] 💚 E2E