[Backport release-3_42] [ux] Fix and harmonize drag and drop in Graduated, Categorized and Point Cloud classification symbol lists #37718

Job	Run time
build (24.04, 5, true, OFF, ON, ON, ON, ON, OFF, OFF, OFF, OFF, ON, false, ON)	35m 29s
build (39, 6, true, ON, OFF, ON, ON, OFF, OFF, ON, ON, ON, OFF, false, ON)	57m 15s
clang-tidy (24.04, 5)	7m 25s
Run tests (5, ALL_BUT_PROVIDERS)	29m 55s
Run tests (5, POSTGRES)	9m 15s
Run tests (5, HANA)	7m 31s
Run tests (5, SQLSERVER)	5m 57s
Run tests (6, ALL_BUT_PROVIDERS)	38m 41s
Run tests (5, ORACLE, 24.04, binary-for-oracle)	6m 58s
	3h 18m 26s

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