[wasm][interpreter] interpreter splat intrinsics fail

[lewing]

The PackSimd.Splat intrinsic definitions is failing lookup because code wasn't setup to handle a scalar arg1

        Console.WriteLine($"These should be the same {PackedSimd.Splat(1)} == {Vector128.Create<int>(1)} (and not kill the runtime)");

demonstration

[lewing]

This should likely be backported once it is resolved

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[lewing]

fixed in #114413