Refactor: VSA vuex root actions and action specs files

The following discussion from !46100 (merged) should be addressed:

• @aturinske started a discussion: (+1 comment)

  Looks good @ekigbo ! Approved! You just need a changelog!

  question (non-blocking): I noticed that the actions.js file is becoming quite large (400+ lines), as well as it's associated spec file (900+ lines); could this feature benefit from this action file being broken up into feature-specific files (e.g. https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/ide/stores/modules/terminal/actions/index.js)?