Metrics-generator: use exemplars from native histograms

[yvrhdn]

Is your feature request related to a problem? Please describe.

While updating a bunch of dependencies in #4466, prometheus/client_golang also got updated. In this update they refactored how native histogram generate exemplars which also changes our usage of native histograms in the metrics-generator. I'm not sure if only our tests need to be updated or also the implementation.

Prometheus PR adding native histogram exemplars: prometheus/client_golang#1471

As a workaround I have disabled NativeHistogramMaxExemplars for now.

Describe the solution you'd like

We should make use of these exemplars but ensure they don't conflict or overlap with classic histograms.

Describe alternatives you've considered

Additional context

Metrics-generator can generate histogram in three modes: classic, native histograms or both. We should make exemplars well work in all 3 modes.