move ManagedRaster into its own module #3501

Job	Run time
Check HISTORY RST syntax	8s
Check for syntax errors	9s
Build sampledata archives	5m 0s
Run model tests (3.8, windows-latest)	13m 43s
Run Workbench Tests (windows-latest)	9m 19s
Run model tests (3.8, macos-latest)	11m 32s
Build binaries (macos-latest)	30m 8s
Run model tests (3.9, windows-latest)	12m 2s
Build binaries (windows-latest)	17m 56s
Check sdist (3.8, windows-latest)	7m 20s
Run model tests (3.9, macos-latest)	15m 6s
Check sdist (3.8, macos-latest)	7m 0s
Run model tests (3.10, windows-latest)	13m 31s
Run Workbench Tests (macos-latest)	4m 15s
Validate Sampledata & User Guide	9m 49s
Run model tests (3.10, macos-latest)	14m 37s
Check sdist (3.9, windows-latest)	6m 27s
Run model tests (3.11, windows-latest)	10m 45s
Check sdist (3.9, macos-latest)	6m 34s
Check sdist (3.10, windows-latest)	7m 18s
Run model tests (3.11, macos-latest)	8m 36s
Check sdist (3.10, macos-latest)	5m 32s
Check sdist (3.11, windows-latest)	7m 20s
Check sdist (3.11, macos-latest)	6m 38s
	3h 50m 45s

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