This commit updates the curl scripts that interact with Kibana's
`api/logstash/pipeline/*` endpoin. Additionally this adds the header to any curl
that interacts with elasticsearch API as well.
This commit changes the serverless tests to use a restricted API key with necessary permissions and disables Logstash legacy monitoring test.
Fixes: #15234
Co-authored-by: João Duarte <jsvd@users.noreply.github.com>