Add SVE2 API skeleton and implement BitwiseClearXor

[snickolls-arm]

This is the first of the SVE2 intrinsics, laying out the test framework and adding the SVE2 API class.

@a74nh @kunalspathak

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[snickolls-arm]

Just need to confirm that this inheritance matches the agreed design, as there was some discrepancy in our code generation scripts? I assumed it should be like this, as the architecture has this dependency and some of the API design issues had this inheritance.

[kunalspathak]

This makes sense to me.

[kunalspathak]

you need to add movprfx if targetReg != op1Reg something like:

                    if (targetReg != op1Reg)
                    {
                        assert(targetReg != op2Reg);

                        GetEmitter()->emitInsSve_R_R(INS_sve_movprfx, EA_SCALABLE, targetReg, op1Reg);
                    }

See how we handle TrigonometricMultiplyAddCoefficient in this file.

[kunalspathak]

And it seems that's why we are seeing test failure too:

Assert failure(PID 60 [0x0000003c], Thread: 60 [0x003c]): Assertion failed 'targetReg == op1Reg' in 'JIT.HardwareIntrinsics.Arm._Sve2.SimpleTernaryOpTest__Sve2_BitwiseClearXor_sbyte:RunLclVarScenario_UnsafeRead():this' during 'Generate code' (IL size 113; hash 0xa6f94412; FullOpts)

    File: /__w/1/s/src/coreclr/jit/hwintrinsiccodegenarm64.cpp:2653
    Image: /root/helix/work/correlation/corerun

[kunalspathak]

I am wondering if there is a need to create Sve2 folder and new project for it or just use existing Sve folder and projects?