Feature Request: Add support for customizing checks cardinality

[jalaziz]

The datadog helm chart exposes datadog.checksCardinality, which ultimately configures DD_CHECKS_TAG_CARDINALITY.

The operation already supports setting tag cardinality for dogstatsd, but a similar configuration for checks appears to be missing.

While we could set the environment variable through overrides, it would be nice to have a higher-level configuration key that sets the environment variable on all the relevant pods.