Add section on internal telemetry to Collector security docs

[tiffany76]

Desired feature or idea: As an iteration on the Collector security docs, we should add a section about internal telemetry.

Additional context: Here are the notes from the section that were removed from the first version of the docs:

Collector's internal telemetry

INSERT RECOMMENDATIONS HERE. For example:

1. Remove zPages. [Explanation]
2. Remove configuration endpoints. [Explanation]

Related to #5209.

[tiffany76]

I'm blocking this until #5209 is merged.