(Editorial) Created a new version for several diagrams

[iherman]

I have re-created the older diagrams with two goals in mind:

• Have some consistency in the "visual language" of the older and newer diagrams (@davidlehn, this was one of your remarks in an older PR)
• All diagrams are now (I hope) dark-mode ready

What dark-mode readiness means:

• Diagrams have a transparent background
• The interior of the various figures (ellipses, rectangles, etc.) are "no-fill", i.e., they are all transparent
• Be careful about colors, because dark mode may mean transforming them into other colors

I have made no change on the diagrams' content. Please, if you review this PR, do not ask here to make a content change on the diagrams; raise a separate issue and I will be happy to take care of it in a separate PR.

All diagrams, except one, are edited using the drawio format. The PR includes both the drawio and the SVG files.

The default preview is useless, because it does not perform the include action. Use the dedicated preview for review.

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Preview | Diff

[msporny]

Editorial, multiple positive reviews, all changes that can be made have been made, no objections, merging.