Add test for the absence of `tags` in apm documents

[simitt]

Problem Statement

We are missing system tests that execute the geo-ip pipeline and then test for it to have succeeded. Any problems with installing the geoip pipeline therefore go unnoticed.

Proposal

Add a check to the integration tests for the event documents to not contain any tags.
Eg. with a current bug, we see following tags in the indexed documents:

  "tags": [
    "_geoip_database_unavailable_GeoLite2-City.mmdb"
  ],

If all pipeline execution succeeds, there shouldn't be any tags, so to avoid overfitting tests to this current example, we should check for the absence of any such tags.

[simitt]

@raultorrecilla for prioritization - the impact for not catching such an issue is for the Geo-location functionalities in the UI to not work properly, which mainly impacts RUM usecases.