Decide what to do about 'Performance basics'

### MDN URL

https://developer.mozilla.org/en-US/docs/Learn/Performance/Web_Performance_Basics

### What specific section or headline is this issue about?

All of it.

### What information was incorrect, unhelpful, or incomplete?

This page lives inside the URL structure for the Learn/Performance module, but isn't properly integrated into the Learn/Performance IA:
- it does not appear in https://developer.mozilla.org/en-US/docs/Learn/Performance#guides, which is the correct place for parts of a Learn module
- it does not appear in the Learn/Performance sidebar
- it has a "Next" link at the top of https://developer.mozilla.org/en-US/docs/Learn/Performance/business_case_for_performance but not at the bottom

Also though, its content does not make sense in the context of the Learn module as a whole. It consists of a collection of performance tips, some of which are covered in detail in other parts of the module, but it doesn't acknowledge any of those other parts.

The history here I think is that https://developer.mozilla.org/en-US/docs/Learn/Performance/Web_Performance_Basics was moved from https://developer.mozilla.org/en-US/docs/Web/Performance/ (in which it was outside the Learn module) into https://developer.mozilla.org/en-US/docs/Learn/Performance, but noone thought to update the nav or consider the content.

I think a real fix here would also address the question of why we have some perf guides at https://developer.mozilla.org/en-US/docs/Web/Performance/ and some at https://developer.mozilla.org/en-US/docs/Learn/Performance. Should we only have one place to teach web perf? If we want two, why, and what's a differentiating factor, and how can we make them work together?

### What did you expect to see?

Coherent content and a consistent nav.

### Do you have any supporting links, references, or citations?

_No response_

### Do you have anything more you want to share?

_No response_