Add routes to allow git actions on snippet repositories

What does this MR do?

In this MR we implement the following:

• Refactors the git_http routes because, for now, snippet repositories won't support LFS (mainly because lfs_enabled is a project feature and we have to think if we could enable it by default for personal snippets).
• It also updates the GitHttpController(s) and the SSH internal API to allow basic cloning/pushing/pulling operations for resources other than projects.

Refs #39176 (closed) Closes #205666 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content

lib/api/helpers/internal_helpers.rb

@@ -104,14 +104,12 @@ def project_path_match
 
       # rubocop:disable Gitlab/ModuleWithInstanceVariables
       def set_project
-        if params[:gl_repository]
-          @subject, @project, @repo_type = Gitlab::GlRepository.parse(params[:gl_repository])
-          @redirected_path = nil
-        elsif params[:project]
-          @subject, @project, @repo_type, @redirected_path = Gitlab::RepoPath.parse(params[:project])
-        else
-          @subject, @project, @repo_type, @redirected_path = nil, nil, nil, nil
-        end
+        @subject, @project, @repo_type, @redirected_path =
+          if params[:gl_repository]
+            Gitlab::GlRepository.parse(params[:gl_repository])
+          elsif params[:project]
+            Gitlab::RepoPath.parse(params[:project])
+          end
       end
       # rubocop:enable Gitlab/ModuleWithInstanceVariables