Support Multistage (YAML) Pipelines

[lmmarsano]

Managing pipelines as code has long been available and is the more modern approach with all the newest features.
However, this code uses variables exclusive to older release pipelines instead of accessing variables available to newer multi-stage pipelines.

keptn-azure-devops-extension/SendKeptnEventTask/index.ts

Lines 553 to 567 in 62b99b1

	if (tl.getVariable("Build.BuildNumber") != undefined){
	labels['buildId'] = tl.getVariable("Build.BuildNumber");
	}
	if (tl.getVariable("Release.DefinitionName") != undefined){
	labels['definition'] = tl.getVariable("Release.DefinitionName");
	}
	if (tl.getVariable("Build.QueuedBy") != undefined){
	labels['runby'] = tl.getVariable("Build.QueuedBy");
	}
	if (tl.getVariable("Release.EnvironmentName") != undefined){
	labels['environment'] = tl.getVariable("Release.EnvironmentName");
	}
	if (tl.getVariable("Release.ReleaseWebURL") != undefined){
	labels['pipeline'] = tl.getVariable("Release.ReleaseWebURL");
	}

I for one would be happy never to see release pipelines again: unnecessary complexity and error-prone, manual labor that misses the ease of writing & tracking a version controlled text file.