[release-20.0] Fix the v19.0.0 release notes and use the vitess/lite image for the MySQL container (#16282)

[vitess-bot]

Description

This is a backport of #16282

[vitess-bot]

Review Checklist

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.59%. Comparing base (cc398e1) to head (e048dc7).

Additional details and impacted files

@@               Coverage Diff                @@
##           release-20.0   #16286      +/-   ##
================================================
+ Coverage         68.58%   68.59%   +0.01%     
================================================
  Files              1541     1541              
  Lines            197814   197814              
================================================
+ Hits             135663   135683      +20     
+ Misses            62151    62131      -20     

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[frouioui]

This PR is based on top of #16287.

EDIT: #16287 is merged, I re-rebased this PR on top of release-20.0.