Improve fly deployment docs

[Martinsos]

[Martinsos]

I (Martin) had hard time learning about wasp deploy fly deploy --skip-server command. In general, I think we could structure the portion of docs that explain deployment to Fly in a more clearly manner, more organized, right now it is a bit messy.

[infomiho]

Docs have been improved, but still no mention of --skip-server https://wasp-lang.dev/docs/advanced/deployment/cli

[Martinsos]

I found this piece of feedback in my notes but I can't remember if it was before or after we restructured docs :D, I will still put it here just in case:

I found Wasp CLI Fly deployment instructions in our docs too verbose, too much info at once. We should better explain setup vs deploy steps.