fix: services are overriding capacity planning defaults rather than compounding

After inspecting the Tamland manifest I noticed that services were missing the environment default from capacity planning default configuration. Turns out the services were overriding the object completely rather than augmenting the defaults.

This had no impact so far, given that we use defaults on Tamland's side, however, we'll soon stop relying on that as we move GitLab.com specifics from Tamland to the manifest to better support Dedicated.

My first intent was to use std.mergePatch here, but since it's not a plain object, it's not possible to do so.