Add README for queueing model analyzer (#893)

* Added readme for queueing model analyzer

* update readme

* update readme

* restructure readme

* moved slo driven queueing model analyzer readme under /docs

* fix: use ScaleTargetAccessor in processInactiveVariant test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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Co-authored-by: tantawi <tantawi@us.ibm.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 3 people