[DOCS] Glossary improvements

[lcawl]

Summary

There are glossaries in multiple locations in our documentation. We ought to converge on a single location (i.e. https://www.elastic.co/guide/en/elastic-stack-glossary/current/terms.html), add any missing terms, then deprecate the following glossaries:

• Elasticsearch Service glossary #2285
• Elasticsearch Add-on for Heroku glossary #2285
• Elastic Cloud Enterprise glossary #2285
• Logstash glossary elastic/logstash#14808
• Security detections terminology #2288, elastic/security-docs#2782