New config option for matplotlib.sphinxext.plot_directive: plot_skip_execution

This configuration option allows users to temporarily skip the execution of all plot directives, not running the code or generating the plots. It is intended to be used during development to speed up building documentation that contains many plot directives.

It can be temporarily enabled from the command line by passing -D plot_skip_execution=1 to sphinx-build, e.g.,: make html O="-D plot_skip_execution=1".