[RFC] Release Plan in 2023 Q2

We are releasing v0.5.0 recently. It is the first release since last year. Next we are going to publish releases as planned. At least one release will be published in 2023 Q2. The planned features are listed below:

- [x] Support the execution service running in Occlum
- [x] Replace the original RPC with tonic gRPC (#668)
- [x] Implement all the services asynchronously

~- [ ] Generate CI code coverage report automatically in CI~

- [x] Secure platform logger aggregator (#669)
- [x] Pick valuable features from `cleanroom` branch to `master` branch

If everything went smoothly, we could work on another release. The possible features are listed below:
~- [ ] Multiple task concurrency in the management and execution service~
- [ ] Enable access control service
- [ ] Support multiple TEE implementations (#460)