In operations/mimir-mixin: Rename rule cluster_namespace_pod:cortex_ingester_ingested_samples_total:rate1m with configuration parameters for cluster and namespace parts (pod is already parameterized).

Idea from Marco: Create configuration parameters similarly to how we define alert_aggregation_variables in operations/mimir-mixin/groups.libsonnet. Copy alert_aggregation_variables logic into a new field called something like alert_aggregation_rule_prefix and change its jsonnet to something like this:

alert_aggregation_rule_prefix:
      std.join(
        '_',
        // Split the configured labels by comma and remove whitespaces.
        std.map(
          function(l) std.strReplace(l, ' ', ''),
          std.split($._config.alert_aggregation_labels, ',')
        ),
      ),