Improve Performance of CBORObject ByteString Decoding

[safestak-keith]

Currently ByteString type CBORObjects are decoded to byte[] using the long form expression

var byteArray = ((string)cborObject.DecodeValueByCborType()).HexToByteArray();

Where DecodeValueByCborType() exists in CBORExtensions.cs as

public static object DecodeValueByCborType(this CBORObject cborObject)
{
    object result = new object();
    switch (cborObject.Type)
    {
      case CBORType.ByteString:
          result = cborObject.ToString().Replace("h", "").Replace("'", "");
          break;
    }
}

This approach is found in hot paths for Transaction CBOR deserialization:

For the CardanoSharp.Wallet SDK to be used in performance-oriented applications we should use the simpler form which doesn't incur additional computation or allocation overhead yet returns same result.

var byteArray = cborObject.GetByteString();

Test to validate equivalence of the approaches

  [Fact]
  public void GetByteStringEquivalence()
  {
      var bytes = new byte[]
          {
             0x01, 0x01, 0x06, 0x00, 0x00, 0x00, 0x3d, 0x1d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
             0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
             0x00, 0x0b, 0x82, 0x01, 0xfc, 0x42, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
          };
      var cborBytestring = CBORObject.FromObject(bytes);
      var decodedFromStringHex = ((string)cborBytestring.DecodeValueByCborType()).HexToByteArray();
      var decodedByteString = cborBytestring.GetByteString();
      Assert.Equal(decodedFromStringHex.Length, decodedByteString.Length);
      for (int i = 0; i < bytes.Length; i++)
      {
          Assert.Equal(bytes[i], decodedFromStringHex[i]);
          Assert.Equal(bytes[i], decodedByteString[i]);
      }
  }