[CAP] Convenience methods for protobuf and some minor refactoring

[rajan-chari]

Why are these changes needed?

1. Sending protobufs requires repeating same boiler plate code
2. Support for non-color console logging

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[thinkall]

Thank you @rajan-chari ! I've just two tiny comments.

Below code:

autogen/samples/apps/cap/py/demo/RemoteAGDemo.py

Line 12 in 24d509c

1) Start Assistant (python demo/standalone/assistant.py)

python demo/standalone/assistant.py should be python demo/standalone/Assistant.py

[qingyun-wu]

Looks good! @rajan-chari It is good to go once Li's comment is addressed! Thanks!

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