Tech debt - metrics vue components are becoming unwieldy

It was noted in a review recently that the area.vue file is very long. I would argue that the same applies to dashboard.vue.

These are heavily used files that affect a large majority of feature work for gitlab-ce10690732 and gitlab-ce10690731 frontend teams.

Problems:

• developer ergonomics. Large files slow reading/scanning and therefore development and increases the chance of unintended interactions causing bugs.
• performance - computed properties will be re-evaluated for unrelated data/prop changes.
• increased chance of merge conflicts.

Solutions:

• Split these two files into smaller components.
• Break out helpers / methods from inside the components into separate files.