Expose conditions to package UI vars

[ChrsMark]

This is mostly applies on kubernetes package and for cluster-level metrics collection using leaderelection. Today we use leaderelection provider of Agent so as to enable specific datastreams of k8s integration only when the Agent holds the leadership lock. This gives as the option to coordinate Agents of the Daemonset so as to have only of them at a time to be collecting cluster-level metrics.

If we are able to deploy Agents on k8s and automatically enrol them to fleet (see elastic/beats#25237) then we should be able to enable k8s integration from Kibana. In order to achieve this we need to separate which datastreams are for all agents and which are only for the leader. To check for leadership we can use a condition (see https://github.com/elastic/beats/blob/2f104b87c851cbffe2b82b05c01b5190e06875c1/deploy/kubernetes/elastic-agent-standalone-kubernetes.yaml#L29) and only enable the datastream if leadership check is true.

For this to happen through the UI we might need to expose the option to define conditions on package level (not hidden behind by default like at https://github.com/elastic/integrations/blob/88b02e1ec40e122fa0de28f4b777cb51b3aba[…]s/linux/data_stream/network_summary/agent/stream/stream.yml.hbs) and have leadership condition there by default for state_* datastreams. Users who do not want to use leadership condition can just remove the default condition and leave the setting blank in the UI input.

Same approach can be used today so as to define conditions based on kubernetes provider which will allow us to enable packages from kibana UI with autodiscovered targets (like https://github.com/elastic/beats/blob/2f104b87c851cbffe2b82b05c01b5190e06875c1/deploy/kubernetes/elastic-agent-standalone-kubernetes.yaml#L338).

cc: @exekias @sorantis @mukeshelastic

[botelastic]

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