[fix] Add copy of label to prevent errors

[RottenRat]

Overview

Fix map reference sharing in MemoryMetricsCollector Set and Add methods by copying labels before storing.

What this PR does / why we need it

MetricsCollector.Set and MetricsCollector.Add stored a direct reference to the labels map passed by the caller. When a hook iterates over multiple objects and reuses the same map (mutating it each iteration), all previously appended MetricOperation entries end up pointing to the same underlying map. As a result, only the last set of labels survives - earlier time series are effectively overwritten.

This PR introduces a copyLabels helper that copies the map before storing it in MetricOperation, ensuring each metric has its own independent label set.

Example of affected hook pattern:

for _, v := range violations {
    metricLabels["violating_object_name"] = v.Name
    input.MetricsCollector.Set(metricName, 1, metricLabels) // same map mutated each iteration
}

After this fix, N violations produce N independent time series in Prometheus as expected.