mcgui/mxgui editable font colors, handle long filenames without extreme window resizing

[willend]

REPLACES #2274

Free-form text area

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

1. Add configuration for (some) mcgui colors in mccode_config, improves visibility e.g. in macOS dark mode.
   (Qscintilla2 editor is not affected by this edit and still does not work too great...) The default colours are these, corresponding to the classical colours of the gui:

• "GUILOGCOLOR": "blue",
• "GUIINFOCOLOR": "green",
• "GUIERRCOLOR": "red",
• Editing for now happens (manually) through gui preferences -> save/edit or mcrun --edit-user-config

2. In case of a long path/filename, add (..long dirname..) as directory and show directory as mouse-over tooltip

• My contribution contains something else

  • Explanation is added in free form text above or below the checklist

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Features partly illustrated here:

• "GUILOGCOLOR": "cyan",
• "GUIINFOCOLOR": "yellow",

• a mouse hovering to reveal a very long path