feat(mimir): Move default data source and final servces to Mimir.
Part of gitlab-com/gl-infra/production#17972 (closed) and gitlab-com/gl-infra/scalability#3442 (closed)
The test dashboards will likely expire before Monday, but they exist today:
Installed https://dashboards.gitlab.net/dashboard/snapshot/UC0mGTp48iwiIEEyCOpef2BXRQ9wFskx - api: Overview Installed https://dashboards.gitlab.net/dashboard/snapshot/2J26aKvg9nanJS5EagHCsHyBxyJkBvZk - errortracking: Overview Installed https://dashboards.gitlab.net/dashboard/snapshot/CriAfNfcSDyxKTSR6iPbvFB9RV8BIOj0 - tracing: Overview