Ensure all jest test suites could be run with @vue/compat

As a first step of preparing our tests codebase for @vue/compat we must ensure that all relevant test suites are at least could be run with Vue.js 3

At the moment there are multiple tests failing due to:

• missing features in vue-test-utils-compat
• template issues with vue.js 3
• unknown stuff

This issue is intended to track progress on making sure that each test suite could be run

Current failures:

• ee/spec/frontend/vue_merge_request_widget/extensions/security_reports/mr_widget_security_reports_spec.js
• spec/frontend/work_items/components/work_item_links/work_item_links_spec.js
• spec/frontend/work_items/components/work_item_links/work_item_link_child_spec.js
• spec/frontend/vue_merge_request_widget/components/widget/widget_spec.js
• spec/frontend/packages_and_registries/package_registry/pages/details_spec.js
• ee/spec/frontend/iterations/components/iteration_cadence_list_item_spec.js
• ee/spec/frontend/diffs/components/diff_view_spec.js
• ee/spec/frontend/diffs/components/app_spec.js
• spec/frontend/pipelines/test_reports/test_suite_table_spec.js
• spec/frontend/pipelines/test_reports/test_reports_spec.js
• spec/frontend/notes/components/notes_app_spec.js
• spec/frontend/notes/components/noteable_discussion_spec.js
• spec/frontend/notes/components/diff_with_note_spec.js
• spec/frontend/diffs/components/diff_view_spec.js
• spec/frontend/diffs/components/diff_file_spec.js
• spec/frontend/diffs/components/diff_content_spec.js
• spec/frontend/diffs/components/diff_discussions_spec.js
• spec/frontend/diffs/components/diff_comment_cell_spec.js
• spec/frontend/diffs/components/app_spec.js
• spec/frontend/artifacts/components/artifacts_table_row_details_spec.js
• spec/frontend/protected_branches/protected_branch_edit_spec.js