Replace HAML fixtures by dynamicly generated HTML fixtures

As mentioned in !6059 (merged) already, the current HAML fixtures have several disadvantages. Namely:

• can not be parsed by JavaScript (because of inline Ruby)
  • requires Rails though tests are run by JavaScript only
  • more difficult to modify fixture files from JavaScript
• are translated into HTML when running tests (solved by #26226 (closed))
  • slows down tests (probably no significant impact)
  • overhead for rerunning tests
  • more difficult to look into HTML
  • HTML can not be downloaded from CI to reproduce errors locally
• overhead of keeping fixtures in sync with application
  • additional effort to update fixtures after app has changed
  • forgetting to update fixture may lead to mistakenly passing tests
  • more necessary work for new tests (decreases motivation for writing tests)
• each fixture correspond to one HAML file
  • many files
  • much duplication (e.g. open issue, closed issue)

Therefore !6059 (merged) introduced a mechanism to generate fixtures using RSpec independently from the testing that happens afterwards.

The following files still need to be translated:

$ bundle exec rspec --format documentation spec/javascripts/fixtures/static_fixtures.rb | grep '\.html\.raw' | sed 's|  static/|- [ ] |'

• abuse_reports.html.haml (!7644 (merged))
• ajax_loading_spinner.html.haml
• application.html.haml (!7318 (merged))
• awards_handler.html.haml (!7661 (merged))
• balsamiq_viewer.html.raw
• behaviors/quick_submit.html.haml ( !9086 (merged))
• behaviors/requires_input.html.haml (!9162 (merged))
• build.html.haml (!7589 (merged))
• comments.html.haml (!7683 (merged))
• dashboard.html.haml (no longer there in 5388f5ee)
• emoji_menu.js (no longer there in 5388f5ee)
• environments/element.html.haml
• environments/environments.html.haml
• environments/environments_folder_view.html.haml
• environments/metrics.html.haml (no longer there in 5388f5ee)
• environments/table.html.haml
• event_filter.html.haml
• gl_dropdown.html.haml
• gl_field_errors.html.haml
• graph.html.raw
• header.html.haml (!9174 (merged))
• issuable.html.haml (!7685 (merged))
• issuable_filter.html.haml
• issue_note.html.haml (!7683 (merged))
• issue_sidebar_label.html.haml (!7688 (closed))
• issues_show.html.haml (!6059 (merged))
• line_highlighter.html.haml
• linked_tabs.html.haml
• merge_requests_show.html.haml
• merge_request_tabs.html.haml (!9172 (merged))
• mini_dropdown_graph.html.haml
• new_branch.html.haml (!9131 (merged))
• notebook_viewer.html.haml
• oauth_remember_me.html.raw
• pdf_viewer.html.raw
• pipeline_graph.html.haml
• pipelines.html.haml
• pipelines_table.html.haml (no longer there in 5388f5ee)
• project_branches.json (no longer there in 5388f5ee)
• projects.json (no longer there in 5388f5ee)
• project_select_combo_button.html.raw
• project_title.html.haml (!9175 (merged))
• right_sidebar.html.haml (!7687 (merged))
• search_autocomplete.html.haml
• signin_tabs.html.haml
• sketch_viewer.html.raw
• target_branch_dropdown.html.haml (no longer there in 5388f5ee)
• todos.json (!9211 (merged))
• u2f/authenticate.html.haml (!8426 (merged))
• u2f/register.html.haml (!8426 (merged))
• zen_mode.html.haml (!7686 (merged))