Upgrades prettier to 1.15.3
Runs `yarn prettier-save-all` against the codebase
Most changes are due to https://github.com/prettier/prettier/pull/5519

This reverts to 2.2.0, which has node@6 compatibility

This upgrades the following packages:
- Vue
- Vue Loader
- Vue Resource
- Vue Router
- Vue template compiler
- Vue Jest

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/53779

This danger check utilises `yarn-deduplicate` in order to show duplicate
dependencies in the yarn.lock dependency tree.
Often when introducing new dependencies or updating existing ones, yarn
does not seem to build the most optimal dependency tree.

In order to prevent those unnecessary dependency updates we are nudging
developers and maintainers to resolve these issues in MRs. Automating
this with danger especially helps, as yarn.lock files are not that easy
to review.

Replace the metrics dashboard graph with
GitLab UI's area chart component

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51210

This suggests possibly related issues when the user types a title.

This uses GraphQL to allow the frontend to request the exact
data that is requires. We also get free caching through the Vue Apollo
plugin.

With this we can include the ability to import .graphql files in JS
and Vue files.
Also we now have the Vue test utils library to make testing
Vue components easier.

Closes #22071