Create a document that describes checks flow that are running on public testnet

Create a document that describes checks flow that are running on public testnet. This will help to validated te checks and possibily improve their flow and test coverage.

Checks running on public-testnet:

```
pt-pingpong,pt-pushsync-chunks,pt-manifest,pt-feed,pt-gsoc,pt-pss,pt-redundancy,pt-retrieval,pt-soc
```