[docs][meta] Improve documentation copied from Beats

[bmorelli25]

Long term meta issue for rethinking/improving the way we copy documentation from the Beats repo.

It is currently very difficult to restructure certain sections of the server documentation. There are a number of issues/PRs related to this:

• Some structure changes here: Reorder docs #1170
  • Example of doc structure conflict: docs: server SSL config is hiding #1579
• Process for updating: Documentation copied from beats #1011

Additionally, there is some restructuring and removal of unused APM conditionals needed in the beats repo

• Beats doc refactoring and restructuring beats#8493

Asciidoctor difficulties:

• Asciidoctor does not support the same if statements that Asciidoc does. The beats repo will need some major refactoring before beats/apm-server can be moved to Asciidoctor. More information: [docs][meta] Migrate APM Server documentation to asciidoctor #1965

[bmorelli25]

We went to the moon in 1969, but 5 years prior, in #1965, we migrated to Asciidoctor. Because of this, we have a bit more freedom in our documentation structure than we once did. We also have a new plan to completely restructure the Observability documentation. I'm closing this one out ✌️