Remove sbyte overloads of Intel AES intrinsics

[fiigii]

Currently, each Aes intrinsic has byte and sbyte overloads, but the unsigned byte is probably sufficient for data encryption/decryption operations.

    public static class Aes 
    {
        public static bool IsSupported { get => IsSupported; }
        public static Vector128<sbyte> Decrypt(Vector128<sbyte> value, Vector128<sbyte> roundKey) => Decrypt(value, roundKey);
        public static Vector128<byte> Decrypt(Vector128<byte> value, Vector128<byte> roundKey) => Decrypt(value, roundKey);
        public static Vector128<sbyte> DecryptLast(Vector128<sbyte> value, Vector128<sbyte> roundKey) => DecryptLast(value, roundKey);
        public static Vector128<byte> DecryptLast(Vector128<byte> value, Vector128<byte> roundKey) => DecryptLast(value, roundKey);
        public static Vector128<sbyte> Encrypt(Vector128<sbyte> value, Vector128<sbyte> roundKey) => Encrypt(value, roundKey);
        public static Vector128<byte> Encrypt(Vector128<byte> value, Vector128<byte> roundKey) => Encrypt(value, roundKey);
        public static Vector128<sbyte> EncryptLast(Vector128<sbyte> value, Vector128<sbyte> roundKey) => EncryptLast(value, roundKey);
        public static Vector128<byte> EncryptLast(Vector128<byte> value, Vector128<byte> roundKey) => EncryptLast(value, roundKey);
        public static Vector128<sbyte> InvisibleMixColumn(Vector128<sbyte> value) => InvisibleMixColumn(value);
        public static Vector128<byte> InvisibleMixColumn(Vector128<byte> value) => InvisibleMixColumn(value);
        public static Vector128<sbyte> KeygenAssist(Vector128<sbyte> value, byte control) => KeygenAssist(value, control);
        public static Vector128<byte> KeygenAssist(Vector128<byte> value, byte control) => KeygenAssist(value, control);
    }

[fiigii]

cc @CarolEidt @tannergooding @eerhardt @mikedn @jkotas

[CarolEidt]

Seems like a good idea to eliminate the sbyte overloads. Do you recall if there was a reason why they were added originally?

[fiigii]

No special reason, we just followed other ISA's convention that expands most of the C++ API (e.g., _mm_unpackhi_epi8 ) to signed and unsigned C# overloads (e.g., UnpackHigh<sbyte> and UnpackHigh<byte>).

[GSPP]

Is there a need to remove them?