R1:8d9bc401e456

Improve Diffusion hosting setup instructions somewhat?

Summary:
Ref T10866. Fixes T10386. This attempts to make it a little more plausible to follow these directions:

- Use simpler language in general.
- Remove language suggesting that HTTP requires no additional configuration.
- Suggest using a load balancer or an ugly port number instead of swapping SSH to a different port.
- Be more granular about `sudo` setup.
- Organize better?

Test Plan: Read documentation.

Reviewers: chad

Reviewed By…