Making py chip-device-ctrl discoverable over DNS-SD as a commissioner

[sharadb-amazon]

Problem

For a Matter Test event, we need to run the python chip-device-ctrl tool on a raspi and test the tv-casting-app against it. For this the tool needs to be discoverable over DNS-SD as a commissioner (It already accepts UDC requests and has the connect command to do onnetwork commissioning)

Change overview

With this change, the python chip-device-ctrl tool will start advertising itself as a commissioner on start-up behind a feature flag: CHIP_DEVICE_CONFIG_ENABLE_COMMISSIONER_DISCOVERY.
TBD: Code to set the flag CHIP_DEVICE_CONFIG_ENABLE_COMMISSIONER_DISCOVERY to 1 for just the python chip-device-ctrl tool will follow separately.

Testing

Tested with the CHIP_DEVICE_CONFIG_ENABLE_COMMISSIONER_DISCOVERY set to 1. Used the minimal-mdns client to ensure the python chip-device-ctrl tool is discoverable as a commissioner device

[msandstedt]

I know we're trying to get things done for test events. But it would be really nice if we addressed some other closely related, underlying issues:

#6141
#7911
#8438
#8722

If we're touching this code, can't some of the above issues get some attention too?

[sharadb-amazon]

#9348 made some significant simplifications to how a commissioner can be advertised. So, the old diff in this PR is moot. Now this PR is just a 4 line change. See 2af778c

[cecille]

I know we're trying to get things done for test events. But it would be really nice if we addressed some other closely related, underlying issues:

#6141
#7911
#8438
#8722

If we're touching this code, can't some of the above issues get some attention too?

Some of those issues are duplicates that were never actually assigned. Ex. multiple operational adverts are supported and have been tested. Please see TestAdvertiser.cpp and TestPlatform.cpp.