Correlate logs to traces

[fmassot]

The elasticsearch plugin allows to define how to link a log to a trace. See the datalinks config part.

We should be able to have the same feature and provide this dataLinks configuration.

Here is a config example coming from the doc:

      dataLinks:
        - datasourceUid: my_jaeger_uid # Target UID needs to be known
          field: traceID
          url: '$${__value.raw}' # Careful about the double "$$" because of env var expansion

To test the setup, we need 2 datasources: one quickwit datasource for the logs and one jaeger datasource for traces.

[idrissneumann]

We need to be able to add the datalink graphically as the elastic datasource

[idrissneumann]

Pull request's ready here: #35