Plane: support `DO_RETURN_PATH_START` mission item and command #18849

Job	Run time
build (check_autotest_options)	1m 9s
build (param_parse)	45s
build (python-cleanliness)	54s
build (astyle-cleanliness)	46s
build (validate_board_list)	36s
build (logger_metadata)	1m 19s
	5m 29s

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