[Fleet] TSDB: add dimension mapping for the dynamic templates

[tetianakravchenko]

Describe the feature:
we need Fleet to support the dimension parameter for the dynamic templates for fields with the type object
Now it is already supported by the Elasticsearch to have a field of type object as a dimension - see elastic/integrations#9400

Describe a specific use case for the feature:
For example - for some integrations (like Prometheus, istio, etc) we need to define labels.* object as a dimension:

    - name: labels.*
      type: object
      object_type: keyword
      dimension: true
      description: |
        Prometheus metric labels

expected dynamic mapping:

{
  "dynamic_templates": [
    {
      "prometheus.labels.*": {
        "path_match": "prometheus.labels.*",
        "match_mapping_type": "string",
        "mapping": {
          "time_series_dimension": true,
          "type": "keyword"
        }
      }
    }
  ]
}

Note: field can't have simultaneously dimension and metric_typedefined

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)