JIT: SVE Cleanup - In the importer, always `ConvertToMask` on SVE APIs that require a mask.

[TIHan]

Discussion: #104704 (comment)

Code:

        if (!varTypeIsMask(op))
        {
            op = gtNewSimdCvtVectorToMaskNode(TYP_MASK, op, simdBaseJitType, simdSize);
        }

The idea is that we shouldn't have to check for varTypeIsMask(op); meaning at this point, op should be returning TYP_SIMD. Therefore, we should always add a ConvertToMask node:

        assert(varTypeIsSIMD(op));
        op = gtNewSimdCvtVectorToMaskNode(TYP_MASK, op, simdBaseJitType, simdSize);

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[a74nh]

priority:3 for RC1 snap : Code is correct but not optimal.