Distributed architecture: Towards the shared log API

[tillrohrmann]

This is an umbrella issue to track the work of implementing the distributed architecture based on the shared log API.

### Tasks
- [ ] Create blog post about how Restate becomes distributed
- [ ] https://github.com/restatedev/restate/issues/1123
- [ ] https://github.com/restatedev/restate/issues/872
- [ ] https://github.com/restatedev/restate/issues/874
- [ ] https://github.com/restatedev/restate/issues/875
- [ ] https://github.com/restatedev/restate/issues/876
- [ ] https://github.com/restatedev/restate/issues/877
- [ ] https://github.com/restatedev/restate/issues/1122
- [ ] https://github.com/restatedev/restate/issues/1280