[tcgc] to provide api for downstream emitters to know if a model is pagedResult

[qiaozha]

Clear and concise description of the problem

In JS modular, we will not expose the @pagedResult models to customers, instead, we will expose an iterator of the itemType in the value list, however, currently, we have no way to know if a model of SdkModelType is pagedResult or not from tcgc,
the only way is to leverage getPagedResult api from compiler, which means we have to use the raw type to get such info.

I wonder if tcgc could help provide apis or extract such info in the SdkModelType for us directly?

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