Add diagram of strategies

[ingvagabund]

Provide diagram with various strategies and the way they operate over pods.

All except LNU (it does not fit properly into the diagram).

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ingvagabund

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [ingvagabund]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ingvagabund]

@damemi @seanmalloy @lixiang233 the diagram is not necessarily a final one. Happy to improve or add more information into it. The goal is to make a high level diagram to show how each strategy works in general. LNU is not included since it does not fit there.

[damemi]

Looks nice, do you want to also add some for the individual strategy sections (or maybe just add one under LNU to explain that a bit more?)

I really like how this fits into the readme though, which is currently a lot of text. Breaking it up with some diagrams will make it more digestable

[seanmalloy]

I think the diagram looks very good. Thanks!

I'll let you work out with @damemi if you want to add more diagrams in this PR or a separate PR.

[seanmalloy]

/kind documentation

[ingvagabund]

Looks nice, do you want to also add some for the individual strategy sections (or maybe just add one under LNU to explain that a bit more?)

I'd like to avoid creating a single diagram for each strategy. Some strategies are quite straightforward to understand (e.g. PodLifeTime, RemovePodsHavingTooManyRestarts, RemovePodsViolatingNodeTaints) and a diagram with a single node and one or two pods would be too simple. Unless each diagram gets more detailed.

Providing more diagrams later sounds better. LowNodeUtilization requires different approach, PodLifeTime's diagram might contain warnings about setting the TTL too low (e.g. in case of VMs), RemovePodsViolatingTopologySpreadConstraint might include soft constraints, etc.

[damemi]

@ingvagabund sounds good to me, yeah everything doesn't need a diagram and this is a great summary of all the strategies working together.
/lgtm