[EPIC] Getting started guide cleanup

[snneji]

Epic to group issues related to the Getting started guide:

• Run through the Getting started guide and create a friction log #4554
• Eventing Getting Started Guide Clarifications #4197
  • clarify that users must follow the guide from start to finish as a tutorial
  • maybe clarify name of guide
• Create a new page for installing the Knative Quickstart #4345
• First Knative Service expected URL is different from the output #4547
• Move Eventing getting started page to getting started guide #4440
• Include minimum system requirements in Getting Started guide(s) #4245
• Getting Started Guide: Show the standard behaviour with server-side generated revisions name #4612
• Reorganise the clean up pages in the tutorial (getting started guide) #4671
• Tutorial commands don't work for minikube #4740

[abrennan89]

Closing this issue since all sub tasks are complete. Any follow up issues re revamping the tutorial can be opened separately.