See T64324 for discussion re improving normal editing ui.
As next step, remove the face_strength tool settings because
menu operator now includes that. Move face_strenth enum to
better place.
Remove normals toolbar panel because only thing left
(normal_vector) can stay hidden for copy/paste.
Remove add vector and multiply vector menu entries as
they are useless without ui method for specifying operand,
and they are very low utility operations anyway.
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