Fixed "configcheck validates ClusterVectorPipeline (CVP) against all ClusterVectorAggregator instances instead of only matching ones"

[P0lskay]

Fixes #201

• Added a check for matching pipeline labels to the vector selector.
• Added tests for functions in internal/utils/k8s/labels.go.
• Moved the matchLabels function to the k8s package.

[aa1ex]

The code panics when Selector is nil:

// Current (crashes when Selector is nil)
if !k8s.MatchLabels(vector.Spec.Selector.MatchLabels, pipelineCR.GetLabels()) {

Fix (same pattern as internal/pipeline/pipeline.go:66-67):

var selectorLabels map[string]string
if vector.Spec.Selector != nil {
    selectorLabels = vector.Spec.Selector.MatchLabels
}
if !k8s.MatchLabels(selectorLabels, pipelineCR.GetLabels()) {
    continue
}

Apply at lines 147, 189, and 238.

[aa1ex]

LGTM