Skip the Network Commissioning cluster on the root node when
CONFIG_CUSTOM_NETWORK_CONFIG is enabled, per Matter spec condition
(!CustomNetworkConfig). This allows devices with out-of-band network
configuration (rich UI, manufacturer-specific means) to omit the
cluster as the spec permits.
- Add CONFIG_CUSTOM_NETWORK_CONFIG Kconfig option
- Conditionally skip network_commissioning in root_node config/add
- Exclude integration.cpp from build when custom config enabled
- Add weak stubs for Plugin callbacks as fallback
- Also guarded secondary network device type and all the
attributes and commands that are part of network commissioning
cluster