COMP: Build against ITK main; repair ExternalData, baselines, and docs CI #868

Job	Run time
build-test-documentation (ubuntu-24.04)	36m 17s
build-test-cxx (windows-2022)	27m 31s
build-test-python-superbuild (macos-15)	24m 18s
build-test-notebooks (windows-2022)	3m 59s
build-test-python-superbuild (ubuntu-24.04)	24m 32s
build-test-notebooks (ubuntu-24.04)	2m 3s
build-test-notebooks (macos-14)	2m 18s
build-test-cxx (macos-14)	13m 38s
build-test-python-superbuild (windows-2022)	24m 22s
build-test-cxx (ubuntu-24.04)	21m 27s
	3h 0m 25s

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