Add metric visibility toggle in project

What does this MR do?

Adds the visibility toggle frontend code behind a feature flag

Issue: #201924 (closed)

Documentation: !29423 (merged)

The feature flag will be shipped OFF by default, to activate it in development issue the following via the rails console

Feature.enable(:metrics_dashboard_visibility_switching_available)

Screenshots

Setting	Recording with the interaction
	Screen_Recording_2020-04-14_at_10.44.49

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides