[API Proposal]: Arm64 SVE: Add LoadAndReplicateToVector for SVE

[a74nh]

Currently there is no obvious way to load a scalar and duplicate it across a vector in SVE. The closest we current have is something similar to:

Vector<uint> vec = Sve.DuplicateSelectedScalarToVector(Sve.LoadVectorNonFaulting(Sve.CreateTrueMaskUInt32(), input), 0);

This is not ideal as it has to load a full vector.

API suggestion:

/// T: float, double, sbyte, short, int, long, byte, ushort, uint, ulong
public static unsafe Vector<T> DuplicateSelectedScalarToVector(Vector<T> mask, T* address); // ld1rb ld1rd ld1rh ld1rsb ld1rsh ld1rsw ld1rw

SVE does not have variants for float, double, long. I assume we can just use the unsigned versions.

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