Platform native support 2 - Support for DQL

[radu-stefan-dt]

Summary
This depends on: Platform native support 1

Details
With version 1.280, extension schema now supports screens for Apps, and these leverage DQL for querying metrics, attributes, and entities. We must not only support it, but also extend all other features to work with these queries.

Sub-tasks for this ticket:

• DQL Code Lens - should provide the same features as the Selector Code Lens. This includes: run DQL query and get its status, run the query and open a webview for visualizing it. We no longer need the JSON output channel here, Strato components can digest entity attributes too.
• Code completions - we have a few code completions that work with entity attributes. Wherever possible we should ensure these keep working on platform too.

Use Cases

• Platform native enablement
• Current SaaS sunset readiness and preparation for DQL in extension schema

Challenges

• There may not be full feature parity between legacy and platform APIs