Add privacy API implementation check to plugin validation requirements

[kabalin]

Depending on MDLSITE-7844 resolution, plugin validation changes are required:

• Validate privacy API presence in MoodlePluginCI\PluginValidate\Requirements\GenericRequirements
• Trigger the core Privacy Provider tests as part of workflow (Privacy Provider Tests by Default #181)

[ngandrass]

Would be awesome to see this integrated. I just had a release that added one userid field to a table but missed defining the field in its privacy provider slip through.