[SuperEditor] Add toggleable headers (Resolves #2276) #2778

Job	Run time
test_goldens_super_editor	1m 28s
test_attributed_text	21s
analyze_super_text_layout	1m 2s
analyze_attributed_text	16s
test_goldens_super_text_layout	1m 5s
test_linux	4m 32s
test_super_editor_markdown	1m 8s
test_mac	6m 1s
test_super_editor_quill	1m 2s
test_super_text_layout	1m 1s
test_windows	5m 38s
	23m 34s

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