add cardinality action plugin

[DmitryRomanov]

Description

Limits the cardinality of fields on events or drops events.

An example for discarding events with high cardinality field:

pipelines:
  example_pipeline:
    ...
    - type: cardinality
      limit: 10
      action: discard
      metric_prefix: service_zone
      key:
        - service
      fields:
        - zone
    ...