reorganize memory, attention, cognitive load

### How could the content be improved?

This suggestion was submitted as #1543 but cannot be merged or edited due to technical difficulties. The improvement to organization suggested by @KwiatkowskiD is as follows:

There are 2 cognitive resources, memory and attention.

Memory - details and how to manage memory
Attention- details and how to manage attention
Overloading either of the creates Cognitive overload.

Cognitive load and discuss strategies to manage cognitive overload.

### Which part of the content does your suggestion apply to?

https://carpentries.github.io/instructor-training/05-memory.html

Start with the lesson at https://carpentries.github.io/instructor-training/05-memory.html and review the existing sections on memory, attention, and cognitive load. Reorganize the content around the two resources and cognitive overload as described; the work is done when the lesson clearly separates these concepts and their management strategies.

Written by the indexing model from the issue text.