[SuperEditor] Add `ClearDocumentRequest` (Resolves #2360) #2864

Job	Run time
test_linux	4m 55s
analyze_attributed_text	17s
analyze_super_text_layout	1m 22s
test_goldens_super_editor	1m 57s
test_attributed_text	20s
test_goldens_super_text_layout	1m 29s
test_mac	6m 35s
test_super_editor_markdown	1m 23s
test_super_editor_quill	1m 23s
test_super_text_layout	1m 19s
test_windows	6m 30s
	27m 30s

Provide feedback