Add import function for ECS component templates

[smnschneider]

Describe the feature:

We already have an option to "Load and activate Elastic prebuilt rules" (https://www.elastic.co/guide/en/security/current/rules-ui-management.html#load-prebuilt-rules).

It would be great to have the same possibility for ECS component templates in any version.

Describe a specific use case for the feature:

For now the only way i know is to get them from GitHub and upload them via curl (https://github.com/elastic/ecs/tree/main/generated/elasticsearch). For customers this is not very handy and makes creating good indices/datastream templates more difficult.

[elasticmachine]

Pinging @elastic/platform-deployment-management (Team:Deployment Management)