Migrate merge conflict views from HAML to Vue SFC

Files affected:

• app/assets/javascripts/merge_conflicts/components/diff_file_editor.js
• app/assets/javascripts/merge_conflicts/components/inline_conflict_lines.js
• app/assets/javascripts/merge_conflicts/components/parallel_conflict_lines.js
• app/views/projects/merge_requests/conflicts/components/_diff_file_editor.html.haml
• app/views/projects/merge_requests/conflicts/components/_inline_conflict_lines.html.haml
• app/assets/javascripts/merge_conflicts/merge_conflicts_bundle.js
• app/views/projects/merge_requests/conflicts/show.html.haml