Clean up exceptions in DAQ betterproto examples

[astarche]

What does this Pull Request accomplish?

Fix DAQ betterproto examples to print better exceptions, especially in common error cases.

Note that betterproto does not report GRPCErrors for connection failures. Those are reported as OSError or TimeouError, which do not provide much structure.

Sample output:

Connection errors (different cases):

> python digital-input-betterproto.py localhost 31763 "gRPCSystemTestDAQ/port0"                                                                                                                                                               
Multiple exceptions: [Errno 10061] Connect call failed ('::1', 31763, 0, 0), [Errno 10061] Connect call failed ('127.0.0.1', 31763)

> python digital-input-betterproto.py 0.0.0.0 31763 "gRPCSystemTestDAQ/port0"                                                                                                                                                                 
[Errno 10049] Connect call failed ('0.0.0.0', 31763)

> python digital-input-betterproto.py 10.0.62.17 31763 "gRPCSystemTestDAQ/port0"
[Errno 10060] Connect call failed ('10.0.62.17', 31763)

UNIMPLEMENTED error:

> python digital-input-betterproto.py 10.0.62.17 31763 "gRPCSystemTestDAQ/port0"
The operation is not implemented or is not supported/enabled in this service

Other GRPC error:

> python digital-input-betterproto.py 10.0.62.17 31763 "gRPCSystemTestDAQ/port0"
GRPCError: (<Status.SOMETHINGELSE: 12345>, None, None)

Error from DAQ/raise_if_error:

> python digital-input-betterproto.py 10.0.62.17 31763 "gRPCSystemTestDAQ/not-a-port"
Error: Device identifier is invalid.

Why should this Pull Request be merged?

Simple implementation to provide reasonable errors for betterproto examples.

What testing has been done?

Ran examples in various success and failure cases.