[skip changelog] Demonstrate the use of the gRPC Settings interface in client_example

[per1234]

• Demonstrate SetValue, Merge, GetValue, and GetAll (added in Add gRPC interface to CLI settings #521).
• Switch from the deprecated configuration request field of Init to using the Settings service to configure arduino-cli's directories.

As requested at #553 (comment)

[per1234]

@andmeyee I've updated client_example as you requested. If you have some time, have a look and let me know if you have any suggestions for improvement.

[andmeyee]

@per1234 thanks for the update. From what I can see in the code everything looks good. But I have to say that I have currently no go runtime installed and am therefore not able to run the code and see if it is fully working. But if you like I can give it a try within the next days.

Using the same gRPC calls from Python is working as expected.

[per1234]

Hi @andmeyee thanks for taking a look at it. Don't feel obligated to set up Go just for this, but if you want to, it would be welcome. I was mostly interested in getting your feedback on whether this change provides a clear example of how to use the Settings interface.

[masci]

Thanks a ton, I completely forgot to update the example 🙇‍♂️