gRPC Server's IVI-Dance has race conditions

[marcoskirsch]

See code in https://github.com/ni/grpc-device/blob/main/generated/nidcpower/nidcpower_service.cpp#L2400

In IVI based APIs, the way clients retrieve strings is by calling the function to get the size, allocating, then calling again with the actual buffer (aka "the IVI Dance").

It is being done incorrectly: the recursive session lock isn't grabbed, so it is possible for the size of the string to grow between the time in which the size is queried and the time in which the string is copied onto the client buffer.

There are two ways to fix it:

1. Acquire the session lock. This is how NI's own C# and Python APIs do it internally.
2. Keep growing the buffer in a loop until it's big enough, which is usually just the one time. This is how NI's own Digital Pattern Editor does it internaly.

AB#1579918