Discard exemplars when forwarding them.

[pstibrany]

What this PR does

This PR modifies forwarder to discard exemplars. In general we should perhaps introduce new option to allow/disable forwarding of exemplars, but for now this works.

Checklist

• Tests updated
• [na] Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[replay]

This makes sense, thanks!
I agree that optimally we would have a configuration option to define whether exemplars should be forwarded, but for now that's not important.

[github-actions]

Helm <> Jsonnet Diff

⚠️ A difference was detected between the Helm chart and the Jsonnet library.

1. Use make check-helm-jsonnet-diff to reproduce the output locally.
2. This test is experimental while we gather feedback about its usefulness.
3. It does not block your PR from being merged, but we would appreciate you trying to keep feature parity between the Helm chart and Jsonnet library if possible.

If you get stuck on this step and the Mimir maintainers aren't able to help, feel free to merge without making this step pass and tag @Logiraptor so the Mimir maintainers can gather feedback later.

Please see the contribution docs here for more info.

Expand to see the output

Output of https://github.com/grafana/mimir/actions/runs/2847626130

Warning: policy/v1beta1 PodDisruptionBudget is deprecated in v1.21+, unavailable in v1.25+; use policy/v1 PodDisruptionBudget
diff -r -u -N scratch/./helm/07-config/ingester-MimirConfig.yml scratch/./jsonnet/08-config/ingester-MimirConfig.yml
--- scratch/./helm/07-config/ingester-MimirConfig.yml	2022-08-12 15:11:42.550522019 +0000
+++ scratch/./jsonnet/08-config/ingester-MimirConfig.yml	2022-08-12 15:11:49.778527895 +0000
@@ -553,7 +553,7 @@
     max_fetched_chunks_per_query: 2000000 (default)
     max_fetched_series_per_query: 0 (default)
     max_global_exemplars_per_user: 0 (default)
-    max_global_series_per_metric: 20000 (default)
+    max_global_series_per_metric: 0
     max_global_series_per_user: 150000 (default)
     max_label_name_length: 1024 (default)
     max_label_names_per_series: 30 (default)
diff -r -u -N scratch/./helm/07-config/overrides-exporter-MimirConfig.yml scratch/./jsonnet/08-config/overrides-exporter-MimirConfig.yml
--- scratch/./helm/07-config/overrides-exporter-MimirConfig.yml	2022-08-12 15:11:42.554522021 +0000
+++ scratch/./jsonnet/08-config/overrides-exporter-MimirConfig.yml	2022-08-12 15:11:49.782527899 +0000
@@ -498,7 +498,7 @@
     max_fetched_chunks_per_query: 2000000 (default)
     max_fetched_series_per_query: 0 (default)
     max_global_exemplars_per_user: 0 (default)
-    max_global_series_per_metric: 20000 (default)
+    max_global_series_per_metric: 0
     max_global_series_per_user: 150000 (default)
     max_label_name_length: 1024 (default)
     max_label_names_per_series: 30 (default)