Avoid GDK.config calls in ERB templates

What does this merge request do and why?

This MR replaces GDK.config with injected config in ERB templates.

It also refactors runit file generation to use existing ErbRenderer.

How to set up and validate locally

gdk reconfigure
# no changes

bundle exec rake clickhouse/users.xml clickhouse/users.d/gdk.xml clickhouse/config.xml clickhouse/config.d/user-directories.xml  clickhouse/config.d/logger.xml  clickhouse/config.d/openssl.xml  clickhouse/config.d/gdk.xml  clickhouse/config.d/data-paths.xml
# Valid configs

Contributes to #2125.

Follow-up MRs will replace the use of GDK.root with gdk_root.

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.