[beats receivers] Introduce new metrics-elastic_agent.collector monitoring data stream

[cmacknz]

Introduce a new monitoring data stream for metrics collected from the embedded or supervised OpenTelemetry collector:

• metrics-elastic_agent.collector.otel-* (may need to be elastic_agent_collector.otel) for OTLP formatted metrics collected from the OpenTelemetry collector.
• metrics-elastic_agent.collector-* for ECS formatted metrics collected from the OpenTelemetry collector. Ideally we can avoid needing both of these but if we do, this will be the convention.

In general follow the convention that OTLP formatted documents have the dataset suffixed with .otel. There are default mappings for .otel suffixed data streams here that may cover this index, if not or if we want to map additional information we will need to define it in the elastic_agent package

Acceptance Criteria

• A test exists confirming that metrics from the collector are ingested into the desired index(es), and that metrics for specific component IDs and names can be queried.

[cmacknz]

One thing to note is metrics-*.otel-* datastreams will have attributes define TSDB dimensions by default so each unique set of attributes is a separate time series.

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)