[Doc] add doc for variant type #43864

Job	Run time
close_msg	2m 10s
Thirdparty Update Image	11s
backport (4.0)	2s
merge_testcase	9s
backport (3.2)	3s
backport (3.5)	2s
backport (3.4)	3s
backport (3.3)	3s
update_backport_merged_msg	0s
update_version_label_for_main_feature	0s
clean_ci_workflow	0s
update_feature_issue	0s
	2m 43s

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