silx.gui.colors: Add "percentile" mode for autoscaling #1699

Job	Run time
Python 3.8 on ubuntu-20.04 PyQt5	10m 40s
Python 3.11 on ubuntu-latest PyQt6	8m 31s
Python 3.12 on ubuntu-latest PySide6	6m 48s
Python 3.10 on macos-13 PyQt5	13m 44s
Python 3.12 on macos-13 PyQt6	15m 27s
Python 3.9 on macos-13 PySide6	12m 54s
Python 3.9 on windows-latest PyQt5	9m 8s
Python 3.12 on windows-latest PyQt6	8m 43s
Python 3.10 on windows-latest PySide6	8m 2s
	1h 33m 57s

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