feat: enhance NewResourceUsageGatherer to support pod label selectors

[sanamsarath]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This pull request introduces changes to the NewResourceUsageGatherer function in the clusterloader2/pkg/measurement/util/gatherers/container_resource_gatherer.go file. The primary focus is to enhance the function by adding support for an optional pod label selector, which allows for more granular pod listing.

Key changes include:

Enhancements to NewResourceUsageGatherer function:

• Added an optional podLabelSelector parameter to the NewResourceUsageGatherer function signature to allow filtering pods by labels.
• Modified the pod listing logic to use the podLabelSelector if provided, enabling the selection of pods based on specific labels.
• Updated the iteration over pods to accommodate the new list structure, ensuring compatibility with the label selector feature.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer: