Support dictionary cmaps for ImageStack #2305

Job	Run time
Run pre-commit	17s
Setup workflow	4s
UI tests on Python 3.9, ubuntu-latest	1m 48s
Unit tests on Python 3.9, ubuntu-latest	25m 46s
Core tests on Python 3.12, ubuntu-latest	4m 37s
Unit tests on Python 3.11, ubuntu-latest	25m 14s
Unit tests on Python 3.9, macos-latest	37m 9s
Unit tests on Python 3.11, macos-latest	50m 39s
Unit tests on Python 3.9, windows-latest	41m 16s
Unit tests on Python 3.11, windows-latest	44m 4s
	3h 50m 54s

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