[docs,wperf] WPERF-1261: Update CMN.md and README to align with latest CMN progress

Introduction

Minor updates to CMN.md and README.md.

In this patch:

• wperf: add wperf.ini docs to CMN.md
• wperf: update CMN.md with latest info (also fix minor typos)
• docs: add CMN-700 and CMN-S3 to README

Testing

Renders are here:

• https://gitlab.com/PrzemekWirkus/windowsperf/-/blob/docs_5_2_0_update/wperf/CMN.md#cmn-mesh-node-isolation-functionality
• https://gitlab.com/PrzemekWirkus/windowsperf/-/blob/docs_5_2_0_update/README.md