Avoid loading Wiki Pages content when listed

This MR adds the method list_pages in ProjectWiki. This method allows listing the wiki pages but without loading their content. This way we can avoid doing it in places we don't need it.

What are the relevant issue numbers?

Closes #53523 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.

app/controllers/projects/wikis_controller.rb

@@ -16,7 +16,7 @@ class Projects::WikisController < Projects::ApplicationController
   end
 
   def pages
-    @wiki_pages = Kaminari.paginate_array(@project_wiki.pages).page(params[:page])
+    @wiki_pages = Kaminari.paginate_array(@project_wiki.pages(load_content: false)).page(params[:page])
     @wiki_entries = WikiPage.group_by_directory(@wiki_pages)
   end
 
@@ -115,7 +115,7 @@ def load_project_wiki
     @sidebar_page = @project_wiki.find_sidebar(params[:version_id])
 
     unless @sidebar_page # Fallback to default sidebar
-      @sidebar_wiki_entries = WikiPage.group_by_directory(@project_wiki.pages(limit: 15))
+      @sidebar_wiki_entries = WikiPage.group_by_directory(@project_wiki.pages(limit: 15, load_content: false))
     end
   rescue ProjectWiki::CouldNotCreateWikiError
     flash[:notice] = "Could not create Wiki Repository at this time. Please try again later."