silx.gui.colors: Add "percentile" mode for autoscaling #1633

Job	Run time
Python 3.8 on ubuntu-20.04 PyQt5 sdist	6m 16s
Python 3.8 on ubuntu-20.04 PyQt5 sdist	6m 16s
Python 3.10 on macos-latest PyQt5 wheel	6m 37s
Python 3.10 on macos-latest PyQt5 wheel	6m 37s
Python 3.8 on ubuntu-latest PySide6 sdist	8m 3s
Python 3.8 on ubuntu-latest PySide6 sdist	8m 3s
Python 3.9 on macos-latest PySide6 wheel	8m 16s
Python 3.9 on macos-latest PySide6 wheel	7m 34s
Python 3.11 on ubuntu-latest PyQt6 wheel	5m 53s
Python 3.11 on ubuntu-latest PyQt6 wheel	5m 53s
Python 3.11 on macos-latest PyQt6 wheel	5m 18s
Python 3.11 on macos-latest PyQt6 wheel	5m 18s
Python 3.9 on windows-latest No GUI wheel	4m 59s
Python 3.9 on windows-latest No GUI wheel	4m 59s
	1h 30m 2s

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