Changes tab VUE refactoring

This MR rewrites diff discussions with VueJS and based on top of the Vue MR discussions.

With this MR, we will render Changes tab and do the diff line commenting with Vue. The current component structure looks like this.

Follow up issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/48034

EE port: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6017

Why was this MR needed?

This is a refactoring so the MR page is based on Vue to support all future developments and also to improve Performance of the page.

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug

• Conform by the code review guidelines

  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer

• Conform by the merge request performance guides

• Conform by the style guides

• If you have multiple commits, please combine them into a few logically organized commits by squashing them

Closes #42882 (closed)