[File based config] Support for Appd

[robsunday]

This is support for AppD context. It includes service name and deployment environment name, as well as business transaction related data.
To make it working use the following snippet:

instrumentation/development:
  java:
    cisco:
      ctx:
        enabled: true

This implementation utilizes BeforeAgentListener to copy service name and deployment environment name from resource attributes to corresponding fields of Appd context propagator. It is implemented this way for two main reasons:

1. Environment variable configuration uses resource customizer for this task. Resource customizers are not available in declarative configuration.
2. Declarative configuration resource detectors are run after all registered DeclarativeConfigurationCustomizerProvider already run. Resource detectors may affect service name and other resource attributes, so our code must run after all the detectors. I'm not aware of any other reliable place to put the code to be executed after SDK is initialized and before any signals are reported.

[robsunday]

[for reviewer] Because we need to check "cisco.ctx.enabled" here, there was no point in getting rid of AppdBonusConfigurationCustomizerProvider class which also checks this property and adds appropriate propagator and span processor.

[robsunday]

[for reviewer] YAML naming convention prefers using underscore, but for consistency with environment variables based config I used hyphen in the name.

[robsunday]

[for reviewer] This will also run when environment variables based configuration is in use. In such a case these propagator's properties are already set by AppdBonusCustomizer. If you think this is an issue I can cleanup AppdBunusCustomizer . This may make sense only if AppdBonusPropagator and span processor are long term solution, not a temporary one.

[laurit]

unneeded ()

[laurit]

Without declarative config we need to add the default propagators. Just checking whether this is also needed here or is it so that when you don't add propagators to yaml then you don't get any default ones?

[robsunday]

Good catch! I missed that. Fixed now

[breedx-splk]

Had a couple small comments, but looks good to me.

[breedx-splk]

The else makes it unnecessarily complex. In the null case, canAddPropagator() will return false anyway.

Suggested change

	if (compositeList == null) {
	compositeList = "";
	} else if (!canAddPropagator(compositeList)) {
	return false;
	}
	if (compositeList == null) {
	compositeList = "";
	}
	if (!canAddPropagator(compositeList)) {
	return false;
	}

[robsunday]

I did even more refactoring and then merged it. Let me know if you don't like it. I can always create another PR