Revamp query builder

[andresmgot]

What happened:

The current query builder is based on custom components created especifically for this plugin. The development there has been stale for quite long so it has become brittle and difficult to maintain.

New and existing plugins are migrating to the new package that https://github.com/grafana/grafana-experimental exposes. We should start migrating the editor here to use the components from there. This should be behind a feature flag (or a version flag) until the builder is moved to the @grafana/ui package or is in the minimum version supported.

What you expected to happen:

To have a standard UX and a query builder easy to maintain.

How to reproduce it (as minimally and precisely as possible):

Screenshots

Anything else we need to know?:

Environment:

• Grafana version:
• Plugin version:
• OS Grafana is installed on:
• User OS & Browser:
• Others:

TODO:

• Query editor header (effort/small)
• Raw query editor (effort/medium)
• Query builder #461