Cherry-pick #19844 to 7.x: Add cache, rows stats and connection errors data to status metricset in MySQL module

[sayden]

Cherry-pick of PR #19844 to 7.x branch. Original message:

What does this PR do?

Adds cache, connection errors and rows stats metrics to the status Metricset in MySQL module as requested in #16955

I'll have to confirm metrics in this PR by the team before attaching any dashboard to avoid modifying it multiple times.

Why is it important?

The enhancement is a step forward to improve the MySQL module.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Implements / Closes [Metricbeat] Revisit MySQL module #16955

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)