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

spec/requests/api/internal/base_spec.rb

@@ -320,7 +320,7 @@
         it 'responds with success' do
           push(key, personal_snippet)
 
-          expect(response).to have_gitlab_http_status(200)
+          expect(response).to have_gitlab_http_status(:ok)
           expect(json_response["status"]).to be_truthy
           expect(json_response["gl_project_path"]).to eq(personal_snippet.repository.full_path)
           expect(json_response["gl_repository"]).to eq("snippet-#{personal_snippet.id}")
@@ -332,7 +332,7 @@
         it 'responds with success' do
           pull(key, personal_snippet)
 
-          expect(response).to have_gitlab_http_status(200)
+          expect(response).to have_gitlab_http_status(:ok)
           expect(json_response["status"]).to be_truthy
           expect(json_response["gl_project_path"]).to eq(personal_snippet.repository.full_path)
           expect(json_response["gl_repository"]).to eq("snippet-#{personal_snippet.id}")
@@ -344,7 +344,7 @@
         it 'responds with success' do
           push(key, project_snippet)
 
-          expect(response).to have_gitlab_http_status(200)
+          expect(response).to have_gitlab_http_status(:ok)
           expect(json_response["status"]).to be_truthy
           expect(json_response["gl_project_path"]).to eq(project_snippet.repository.full_path)
           expect(json_response["gl_repository"]).to eq("snippet-#{project_snippet.id}")
@@ -356,7 +356,7 @@
         it 'responds with success' do
           pull(key, project_snippet)
 
-          expect(response).to have_gitlab_http_status(200)
+          expect(response).to have_gitlab_http_status(:ok)
           expect(json_response["status"]).to be_truthy
           expect(json_response["gl_project_path"]).to eq(project_snippet.repository.full_path)
           expect(json_response["gl_repository"]).to eq("snippet-#{project_snippet.id}")