Resolve "Utilize new charting library for metrics dashboard"
What does this MR do?
Begins the migration process away from D3 and towards ECharts for our metrics dashboard graphs:
- Integrates GitLab UI Area chart
Does not address the following (needed before we can remove the feature flag):
- the need to integrate deployment data: https://gitlab.com/gitlab-org/gitlab-ce/issues/54973
- the ability to set thresholds: https://gitlab.com/gitlab-org/gitlab-ce/issues/54974
- updating tests