matplotlib-pgfutils 2.0.0

This is a major release. The main operation of the script should be largely backwards-compatible, but the configuration file now uses the TOML format instead of the custom INI-based format of previous versions. Some configuration sections have been moved, and the ability to output tracked files to stderr has been removed as it often got corrupted with Python warning messages.

The minimum officially supported Python version is now 3.12, and the minimum officially supported Matplotlib version is now 3.9.0.

The main new feature in this release is the ability to extract the legends from figures and save them as separate files. This can be used, for example, to place legends in the margins of a document next to the figures. This must be enabled with the separate_legends setting.