[TSDB] Need Indicators for dimension fields when TSDB is enabled.

[agithomas]

Describe the feature:

It is a tedious process for a user to identify a dimension field / dimension fields once TSDB is enabled.

It is an important field to learn and make changes if needed. It would be good if an icon can be added next to the fields in the Discover detailed document view in addition to the icons that displays keyword

Reference : elastic/integrations#4848

Describe a specific use case for the feature:
Indicators can help for problem debugging such as missing data
Indicators can help to identify the dimension fields that can be used to create aggregation

[ruflin]

++ on having this indication in discovery. I assume field caps exposes that it is a dimension.

This here might be related, as in the screenshot on this page there is a t for dimensions for the field list: #130726

[ruflin]

Ideally the same icon could also be used in our field docs for integrations: elastic/elastic-package#1127