[Bug]: Template parameters cannot be used in object/array values, even if they are constrained

[witemple-msft]

Describe the bug

The checker doesn't currently allow template parameters to be used in array or object value contexts, even if they are constrained to valueof.

I suspect this has to do with decorator argument checking.

Reproduction

https://typespec.io/playground/?c=CmV4dGVybiBkZWMgZm9vKHRhcmdldDogUmVmbGVjdGlvbi5Nb2RlbCwgb3DEDnM6IHZhbHVlb2YgeyB2OiBzdHJpbmc7IH0pOwrMTGJhcttMYXJny0nGRFtdxENA5ACFI8VbViB9KccQW1ZdKQptxDwgWDxWIMRobmRzz0E%2BIHt9&e=%40typespec%2Fopenapi3&options=%7B%7D

Checklist

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• The provided reproduction is a minimal reproducible example of the bug.

[timotheeguerin]

Thought this was a simple fix where we could just ignore the value in those case and return null (which is the equivalent to ErrorType for values) but this then makes it that it won't do type checking further (if the value constraint would create an incompatible type)

Initial idea in this branch(https://github.com/microsoft/typespec/tree/tenative-fix-template-values) this would also fix the using default value in template if it worked i think

[markcowl]

To the extent this blocks a 1.0 feature like MergePatch, this should be in 1.0, otherwise this can be moved later