Fix accessing undefined properties on Vue instances for Vue 3 migration

What does this MR do and why?

This MR fixes unit tests failures for VUE_VERSION=3. These failures were happening due to missing component instances

• Property "humanizedTitle" was accessed during render but is not defined on instance.

  • spec/frontend/integrations/edit/components/dynamic_field_spec.js

• Property "discussion" was accessed during render but is not defined on instance.

  • spec/frontend/notes/components/noteable_note_spec.js
  • spec/frontend/notes/components/noteable_discussion_spec.js
  • spec/frontend/diffs/components/diff_discussions_spec.js

• Property "$store" was accessed during render but is not defined on instance.

  • ee/spec/frontend/usage_quotas/seats/components/subscription_usage_statistics_card_spec.js
  • spec/frontend/analytics/cycle_analytics/components/filter_bar_spec.js
  • ee/spec/frontend/analytics/code_review_analytics/components/filter_bar_spec.js
  • spec/frontend/ide/components/commit_sidebar/new_merge_request_option_spec.js
  • ee/spec/frontend/boards/components/issues_lane_list_spec.js

• Property "tertiaryButtons" was accessed during render but is not defined on instance.

  • ee/spec/frontend/vue_merge_request_widget/extensions/security_reports/index_spec.js
  • ee/spec/frontend/vue_merge_request_widget/extensions/browser_performance/index_spec.js
  • ee/spec/frontend/vue_merge_request_widget/extensions/load_performance/index_spec.js
  • spec/frontend/vue_merge_request_widget/extentions/accessibility/index_spec.js

Screenshots or screen recordings

No visual changes

How to set up and validate locally

Run all the mentioned specs with VUE_VERSION=3 flag

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.