Context:

As Elasticsearch 7.14 & 7.15 got release we should add it to the supported versions.

AT:

• Elasticsearch 7.14 & 7.15 is added to supported versions
• the supported environment docs are updated
• the integration test pipeline has a stage for Elastic 7.14 & 7.15
• the support of 7.14 & 7.15 is mentioned in the support announcements https://docs.camunda.org/enterprise/announcement/