allow annotate_grids to force cmap to respect max_levels

[zingale]

PR Summary

At the moment, when you use annotate_grids() to show boxes and compare simulations with different
numbers of refinement levels, the colors don't correspond to one another across simulations. For example,
here are 4 different simulations. One has base + 1 level, then next 2 levels, then 3, and finally 4 levels of refinement
(all are jumps of 2x). Notice that the color for level 1 is not the same across all simulations:

Here's the output with this PR if I pass use_max_level_in_cmap=True to annocate_grids().

Note: I am unsure why the original behavior was desired, but I left it in place.

PR Checklist

• New features are documented, with docstrings and narrative docs
• Adds a test for any bugs fixed. Adds tests for new features.

[neutrinoceros]

Although the change is simple, I'm not sure I understand the approach: it would seem reasonable to me to consider the current behaviour is buggy; within this framing, I think we don't need to keep "backward compatibility", so the introduction of a new argument seems superfluous.

If anyone can convince me that I'm being mislead and that we do need to preserve existing behaviour, then I'd strongly recommend that any new argument (especially booleans) be made keyword only and documented.

[zingale]

I also don't understand the current way it works, but I didn't want to remove it in case someone was relying on "spacebar heating"

[neutrinoceros]

Nice reference !
I think we could use a third pair of eyes here. As far as I am concerned, I feel like this kind of "breaking" change could even be acceptable if shipped in a feature release. Let's aim this at the upcoming 4.3 release and see what others think !

[matthewturk]

Yeah, we can remove the old behavior, I think. Thanks for submitting this!

[zingale]

okay, I'll update the PR to just change the current behavior

[neutrinoceros]

Thanks @matthewturk and @zingale !