[Streams] Adding the first integration test

[simianhacker]

Summary

This PR introduces the first integration test for the Streams project. This test covers the following basic functionality:

• Enable streams
• Index a document to logs
• Create a logs.nginx for that reroutes based on log.logger == 'nginx'
• Index a document to logs.nginx
• Create a logs.nginx.access that reroutes based on log.level == 'info'
• Index a document to log.nginx.access

[elasticmachine]

:yellow_heart: Build succeeded, but was flaky

• Buildkite Build
• Commit: fb67217395cf5772705c65bddc808111b6a72f10

Failed CI Steps

• Jest Tests #13

Test Failures

• [job] [logs] Jest Tests #13 / OutputHealth should render output health component when degraded

Metrics [docs]

✅ unchanged