fix the union type document issue

[ArcturusZhang]

Fixes #4508
Fixes #4509

Description

We construct a message in xml doc on a property when the its type is related with BinaryData, including when the type is BinaryData, or the type is a collection type of BinaryData.
Previously the code was not written in a recursive way so that the generator only adds messages when the type is IDictionary<string, BinaryData> or IList<BinaryData>. It does not recognize more complicated cases such as IDictionary<string, IList<BinaryData>>, we are having this case in the additional properties cadl ranch cases.

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