[CECO-941][docs] Add introspection docs

[khewonc]

What does this PR do?

Add public docs about introspection

Motivation

What inspired you to submit this pull request?

Additional Notes

Anything else we should know when reviewing?

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Agent: n/a
• Cluster Agent: n/a

Describe your test plan

Write there any instructions and details you may have to test your PR.

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[hestonhoffman]

Couple small edits

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6f5b5c5) 58.58% compared to head (3a00249) 58.63%.
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1069      +/-   ##
==========================================
+ Coverage   58.58%   58.63%   +0.04%     
==========================================
  Files         166      166              
  Lines       20513    20631     +118     
==========================================
+ Hits        12018    12097      +79     
- Misses       7767     7808      +41     
+ Partials      728      726       -2     

Flag	Coverage Δ
unittests	58.63% <ø> (+0.04%)	⬆️

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see 8 files with indirect coverage changes

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