vector serialization does not take into account endianness

The [gRPC protocol is defined](https://github.com/ansys/api-eigen-example/blob/108085fcaa860a9d1e27abbdc561c160a98e09e3/src/ansys/eigen/protos/grpcdemo.proto#L21) as sending over the bytes of arrays directly, but does not take into account endianness. This means the protocol will fail spectacularly (type 3 error, bad data with no error) if the client and server machines have different native endianness.

https://github.com/ansys/api-eigen-example/blob/108085fcaa860a9d1e27abbdc561c160a98e09e3/src/ansys/eigen/cpp/grpc/client/src/GRPCClient.cpp#L499

https://github.com/ansys/api-eigen-example/blob/108085fcaa860a9d1e27abbdc561c160a98e09e3/src/ansys/eigen/python/grpc/client.py#L280

Unless there is another reason, I recommend using gRPC arrays instead of bytes. gRPC can handle this for us.

Start with the referenced grpcdemo.proto definition and the serialization points in src/ansys/eigen/cpp/grpc/client/src/GRPCClient.cpp and src/ansys/eigen/python/grpc/client.py. Compare the current bytes-based representation with gRPC arrays and determine the cross-endianness behavior that must be preserved. Done means clients and servers with different native endianness exchange vector data without silent corruption.

Written by the indexing model from the issue text.