Fix plotting-related warnings

Description

There were deprecation warnings popping up in the darks notebooks, caused by cal_tools.plotting.show_overview. I don't like warnings, so I changed the rcParams and updated the colorbar instantiation as some matplotlib documentation indicated.

Also, the logic handling label colors and colorbar labels for each subplots was a bit buggy, so I fixed that.

How Has This Been Tested?

In the AGIPD darks notebook, I inserted the updated function definition and re-ran the cell. It looked fine. I also shuffled around the order to ensure that the labels get colored appropriately.

Old plot:

• Note the wrong label on the bad pixels colorbar
• Label on bad pixels subplot is white and so invisible (hopefully, otherwise we have many bad pixels)
• Weird logarithm of bad pixel codes - probably because NaN is plotted as white which gives good contrast?

New plot:

• Labels fixed
• Still has weird logarithm on bad pixel codes

New new plot:

• Now bad pixel plot is just white 0 for "good", black 1 for "bad" instead of weird logarithm

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the code style of this project.

• I have not added tests where appropriate :(

Reviewers

@calibration

If no complaints come up, will merge later today.