Improve context for each of the steps of the YAML-based install

[omerbensaadon]

What is changing? (Please include as many details as possible.)

Currently, the steps in the YAML-based install are devoid of context. Examples below:

1. 
2. 

Ideally, each of these sections would have a bit of information about what you are doing to your cluster and why you may want to follow that step in the installation process.

Context

During the "Getting Started" interviews, we heard from many users that the installation process for Knative was frustrating.

Networking, for example, was a massive friction point for many users. Many did not understand which networking layer they ought to use and our defaulting to Istio was a nudge to folks that we were "recommending" it as the default networking layer.

We also heard comments to the effect of "I did the install but I had no idea what I did" which is a smell that we may be giving people a bunch of terminal commands without sufficient context.

How will this impact Knative users?

Adding more context to the different steps in the installation will help make more users successful.

Prototype

Each of the subheadings on https://knative.dev/development/install/any-kubernetes-cluster/ ought to have additional context associated with them as well as links out to explanatory docs if they exist.

More specific prototypes to be attached to child issues.

Potential Feature List

• Add YAML description to each of the files under "Installing Serving Component;" explain why each is needed and what it enables the user to do
  ^^ See Add YAML description to each of the files under "Installing Serving Component" (development/install/any-kubernetes-cluster.md) docs#3376 ^^
• Add context as to why the user needs to add a Networking layer, add a recommended Networking layer for prototyping
  ^^ See Add context as to why users need to add a Networking layer, add a recommendation for prototyping (development/install/any-kubernetes-cluster.md) docs#3377 ^^
• Add YAML description to each of the files under "Installing the Eventing component;" explain why each is needed and what it enables the user to do
  ^^ See Add YAML description to each of the files under "Installing Eventing Component" (development/install/any-kubernetes-cluster.md) #3376 docs#3378 ^^
• Add context as to why the user would need a Channel layer, what it can do, what it's dependencies are; add collapsable explanation of channels which reflects the contents of https://knative.dev/development/eventing/channels/
• Add context as to why the user would need a Broker layer, what it can do, what it's dependencies are; add collapsable explanation of channels which reflects the contents of https://knative.dev/development/eventing/broker/

[omerbensaadon]

@snneji is this sort of what we were talking about in knative/docs#3361?

Feel free to make an issue out of any one of these in the docs repo if you get to it before I do!

[omerbensaadon]

Add YAML description to each of the files under "Installing Serving Component;" explain why each is needed and what it enables the user to do

Done in knative/docs#3376

[omerbensaadon]

Add context as to why the user needs to add a Networking layer, add a recommended Networking layer for prototyping

Done in knative/docs#3377

[omerbensaadon]

Add YAML description to each of the files under "Installing the Eventing component;" explain why each is needed and what it enables the user to do

Done in knative/docs#3378

[omerbensaadon]

Going to call this done