E2E - Version control for snippets - Part 2

What does this MR do?

Creates an end-to-end to test version control for project snippets as per #207110 (closed)

This is Part 2 of a split MR, for Part 1 see !28068 (merged). Part 2 includes test cases for project snippets:

• Clone/push/pull a project snippet over HTTP - create & edit via UI
• Clone/push/pull a project snippet over SSH - create & delete via UI

To run the tests:

CHROME_HEADLESS=false bundle exec bin/qa Test::Instance::All http://localhost:3000 -- qa/specs/features/browser_ui/3_create/snippet/clone_push_pull_project_snippet_spec.rb

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content