[BUG] NDM Autodisovery in datadog.yaml breaks when using ignored_ip_addresses

[a-rhodes]

Agent Environment
Tested Versions: 7.57.2 & 7.57.0

Bug was introduced in 7.54.0 when network_devices.autodiscovery was added to datadog.yaml

Describe what happened:
When using the ignored_ip_addresses feature of network_devices.autodiscovery.configs, the SNMP Listener will fail to start and no network devices will be monitored.

Describe what you expected:
Expect ignored_ip_addresses to work as documented.

Steps to reproduce the issue:
Add a network_devices config to datadog.yaml:

network_devices:
  autodiscovery:
    loader: core
    configs:
      - network_address: 192.168.0.1/30
        snmp_version: 2
        port: 161
        community_string: public
        ignored_ip_addresses:
          - 192.168.0.2

No log for Configs for autodiscovery detected: Adding the snmp listener or snmp listener successfully started in agent.log

Additional environment details (Operating System, Cloud provider, etc):
Here is a PR with a unit test showing the failure: #30177
Here is a PR with a fix and a new unit test: #30180

The issue comes down to the YAML Unmarshal. It is documented that the config item ignored_ip_addresses should be a list of IPs as strings, but the struct for the config expects a map[string]bool. In the primary autodiscovery code, it calls snmp.NewListenerConfig()
https://github.com/DataDog/datadog-agent/blob/main/comp/core/autodiscovery/listeners/snmp.go#L71
Which has a special hook for converting lists to maps:
https://github.com/DataDog/datadog-agent/blob/main/pkg/snmp/snmp.go#L101-L117

But, when the agent starts and tries to add the listener, it attempts to load the config without this hook, and as such the configuration fails to load and the listener is not added. The error is also not logged, so the user has no idea why it's failing:

datadog-agent/pkg/config/autodiscovery/autodiscovery.go

Lines 77 to 84 in 122c53f

	// Auto-activate autodiscovery without listeners: - snmp
	configs := []snmplistener.Config{}
	err := pkgconfigsetup.Datadog().UnmarshalKey("network_devices.autodiscovery.configs", &configs)
	if err == nil && len(configs) > 0 {
	detectedListeners = append(detectedListeners, pkgconfigsetup.Listeners{Name: "snmp"})
	log.Info("Configs for autodiscovery detected: Adding the snmp listener")
	}