Speed up execution of mcplot-matplotlib (especially for big 2D matrices)

[willend]

Free-form text area

Please describe what your PR is adding in terms of features or bugfixes:

Simple drop-in replacement of pcolor() -> pylab.pcolormesh() in matplotlib-plotter.

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Declaration of use of AI-tools

• Please add a checkmark here if you used AI-tools during the work for this contribution
• Furter, please describe how / where and for what the tools were used:

I did use Claude for this suggestion, but change is so compact and simple that I will proceed to merge without full rigour of review etc.

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Development OS / boundary conditions

Please describe what OS you developed and tested your additions on, and if any special dependencies are required:

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• My contribution contains something else

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