Updates behavior when new session name is in use in different resource repository.

[reckenro]

What does this Pull Request accomplish?

• Created a new SessionException struct in the shared library
• Throw a SessionException from the session resource repository when trying to add a session that's already in a different resource repository instead of returning a warning status of 1.
• Update codegen so all "Init" service handlers catch the new SessionException and return a gRPC Status of INVALID_ARGUMENT with the exception's message attached.
• Update the session resource repository unit test to now expect the SessionException to be thrown when trying to add a session where the session name is already in use in a different resource repository.

Why should this Pull Request be merged?

Addresses #685

If a proposed session name is already used by a different driver, grpc-device was returning a warning status 1 on the return message's status field. This both allows programs making the call to keep running since it's treated as a warning and if the client does check the status code it can be ambiguous depending on the driver.

This change addresses this by instead immediately returning a gRPC Status of INVALID_ARGUMENT with a message explaining that the session name is already in use.

What testing has been done?

Updated a unit test testing the old behavior to now ensure the new SessionException is thrown if the session name is used in a different resource repository.

Ran the examples like they were specified in the Issue.

Now, running the daqmx example while dcpower is running using "my task" as the session name produces:

PS ~\grpc-device\examples\nidaqmx> python .\analog-input.py
The session name "my task" is being used by a different driver.

And similarly, running the dcpower example while the daqmx example is running (with time.wait(60.0)) stops the program with the same message:

PS ~\grpc-device\examples\nidcpower> python .\measure-record.py
The session name "my task" is being used by a different driver.

[astarche]

Nice fix!

[astarche]

@reckenro I added the breaking change tag here. The old behavior was pretty wrong and a bit of an edge/probably-a-mistake case anyway. But (I think) it's possible that someone could have worked around the old behavior in a way that would now break.