Audit and document applies_to dimensions in Troubleshooting and Reference sections

### Collaboration model

### Point of contact.

**Main contact:** @elastic/docs-tech-leads

### Description

Conduct a thorough scan of the Troubleshooting and Reference sections of the Elastic docs to identify the best 'applies_to' dimensions to use across pages.

### Which deployment methods does this change impact?

### Feature differences

### Resources

Slack thread context: review how 'applies_to' tags and classification are used, as shared by Ty and others, to reduce confusion and improve relevance. See historical drift/migration note: https://github.com/elastic/docs-content/pull/6634/changes and https://github.com/elastic/docs-content/commit/82f92dd580025851b8ef2a7ab070b89482e319c9.

### Serverless release

### What Elastic Stack release is this request related to?

[View original Slack conversation](https://elastic.slack.com/archives/C05PP2LEC1X/p1779381341753069?thread_ts=1779381341.753069&cid=C05PP2LEC1X)