Explore creating a feature flag or configuration for Apache Analytics on docs-core

### Issue description

See: https://github.com/apache/grails-core/pull/14842/files/a5d7343993ca2d9cac84c86ec5ea79350014b275#diff-c5c8fea4151e17da041f6f6fb87c8664efe5b05432b2c6e14ed43e3b02bbedb6

Should Apache Analytics be added to any plugin using the publish guide templates? Historically the Grails Google Analytics code was added.

Start with the linked pull request diff and inspect the publish guide templates in docs-core, including the historical Google Analytics code. Determine whether Apache Analytics belongs in plugins using those templates and what feature flag or configuration scope would be required; done means a documented decision and an agreed implementation path.

Written by the indexing model from the issue text.