Add high-cardinality HTTP duration label value

[aliaqel-stripe]

Provide a description of what has been changed

This adds operator.enableHighCardinalityMetricsLabels to the KEDA Helm chart.

The value defaults to false, matching KEDA core, and wires the --enable-high-cardinality-metrics-labels flag through to the operator deployment. When enabled, scaler HTTP request duration metrics include the high-cardinality namespace, scaled_resource, trigger_name, and metric_name labels/attributes.

The previous metrics-server value and argument were removed because internal Metrics Service gRPC histograms are no longer gated by this flag.

Relates to kedacore/keda#7751

Checklist

• I have verified that my change is according to the deprecations & breaking changes policy
• Commits are signed with Developer Certificate of Origin (DCO - learn more)
• README is updated with new configuration values (if applicable) learn more
• A PR is opened to update KEDA core (repo) (if applicable, ie. when deployment manifests are modified)

Fixes #