[Bug]: Models assigned where constraint is mix of "value unknown" and "unknown" throws deprecation warning

[chrisradek]

Describe the bug

With the introduction of the new values syntax, parameters are treated as values over types if a constraint supports both.
This was done intentionally for scalar literal values.

However, this change also causes model expressions and tuples to show a deprecation warning when passed somewhere (model template parameter/decorator) where they can be interpreted as either a Type or a Value. TypeSpec should still allow using tuples/model expressions as types when constraints are mixed.

Reproduction

playground link

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