Add forbidden entity functionality [#3320812]

Some entities should not be allowed to be used. Allow plugins to forbid entities.

Add a method to EntityAuthBase to allow plugins to override and forbid entities from auth.

New overridable method.

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entity_auth-3320812-3320812-add-forbidden-entity changes, plain diff MR !7
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3320812-add-forbidden-entity changes, plain diff MR !6
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