Add support for collections in all namespaces

[lcarva]

Today, collections are widely used in the policies under the release namespace. The docs know how to display them. This is nice.

This issue is about adding the same level of support for all namespaces (or at a bare minimum to the task namespace.) If we try to do that today, the website fails to build with an obscure error:

[15:46:50.902] FATAL (antora): Cannot read properties of undefined (reading 'title')

This seems to originate from here.

Acceptance Criteria

• When using collections in the policy rules from the task namespace, the website build does not break and they are properly described in the website.
• Revert Remove collections from step image registries #873
• As a stretch goal, make this true for all namespaces.