Auto-generation support for daqmx streaming apis

[Raghav-NI]

What does this Pull Request accomplish?

This PR adds support for auto-generation of DAQmx streaming APIs.

Why should this Pull Request be merged?

• Updated metadata for DAQmx functions to include additional information regarding streaming.
• Added custom_proto.mako which defines protobuf message definitions to encapsulate different data types for DAQmx apis.
• Modified logic in service_helpers.mako to auto-generate the streaming function bodies.
• Modified service_helpers.py and common_helpers.py to generate the correct function structure for streaming apis.
• Removed few unnecessary whitespaces from nifpga_service.cpp.

What testing has been done?

I am able to build the server code without any errors and able to use the client call and call the server with all the new streaming APIs.

[astarche]

Nit: the list comprehension for selecting output_params is much cleaner than the loop for selecting streaming params. Using list comprehensions and helper methods makes a big difference:

def is_streaming_param_except_name(param, name_to_avoid_for_some_reason):
   # TODO why avoid name_to_avoid_for_some_reason?
   param.get("is_streaming_type", False) and param["name"] != name_to_avoid_for_some_reason

def get_output_streaming_params_to_define(parameters, streaming_param) -> List[dict]:
    """Get the list of output streaming parameter that needs to be defined."""
    output_params = [p for p in parameters if common_helpers.is_output_parameter(p)]
    return [p for p in output_params if is_streaming_param(p, streaming_param["name"])]

Actually, rewriting this, I realize I don't understand this code. We're avoiding one specific streaming parameter? Why is it not sufficient to look for is_output_parameter and is_streaming_type? Is streaming_param named correctly?

[Raghav-NI]

The reason behind avoiding that specific parameter is that it is the 'first' streaming parameter (eg: readarray), here we want to define other params which will be part of the response message for streaming apis. (eg: samp_per_chan_read).
And yes, it should be named as "first_streaming_param" to avoid confusion.

Modified to use list comprehensions and a helper method and renamed the parameter.