DBaaS: Change from Dashboard to Grafana Page

What should be done:

• Migrate DBaaS from Grafana Dashboard to Grafana Page
• Make the page accessible only if DBaaS is activated in PMM (Env variable or Setting later. The same way how it's activated for Left menu)

Why:

• To eliminate confusion with the presence of this part in the menu.
• Make UI for the page free from "grafana panels artifacts"

Benefit:

• User will not be confused by ever seeing this DBaaS in the list of dashboards even if DBaaS will be activated

Details:

Ticket affects only DBaaS