Allow users to specify dataset and namespace for rerouting data collected by kubernetes.container_logs datastream

[gsantoro]

As a follow-up of #5988 we want to avoid adding default routing rules in our integrations. Instead, we would like to give the user the ability to specify labels in Kubernetes containers that would be used to reroute the traffic.

In contrast to previous considerations, we’re not creating a data stream per service name as this would lead to a lot of overhead for customers with thousands of services.

The reroute processor was introduced in this PR elastic/elasticsearch#76511 and it has been available since 8.8.0.

Currently, you can add the reroute processor manually to an ingest pipeline with an if condition to reroute traffic to a destination dataset and namespace.

This is a quite manual process at the moment.

In order to improve the experience for the end user we could:

1. Define some standard Kubernetes labels (for example elastic.co/dataset and elastic.co/namespace) that if present could be used to reroute the traffic automatically without the need to define a custom pipeline defined by the user. The values from those labels would end up into the fields data_stream.dataset and data_stream.namespace and a default routing rule will use them to reroute the traffic. Since the reroute processor has to be added to an ingest pipeline, that means that integrations that use those Kubernetes labels should have an ingest pipeline that checks for the presence of those container labels and reroute if those are present. We will have to evaluate what's the performance hit of having these extra steps always running. Since the benefits are quite significant, maybe that's worth it.
2. we should also extract the fields service.name and service.version from the well knows Kubernetes labels app.kubernetes.io/name and app.kubernetes.io/version. Alternatively if those are not provided we should infer the service name from the field container.name and leave out the service.version field.

[felixbarny]

This is unblocked now that specifying local routing rules are supported in the package spec and in Fleet

• [Fleet] Add support for routing rules in integrations package-spec#514
• [Fleet] Support local routing rules during integration installation kibana#155910

The minimum stack version has to be set to 8.10, though, as that's the version where Fleet supports that feature.