Add SRG DQL variable support

[drqc]

The new version of SRG allows you to use variables in the DQL expressions, this can be part of the payload that gets send using the cli.

Tasks:

• Research how the new feature works and what is the expected format of the payload
• Modify the existing payload to include this variables
• Document the new functionality

[drqc]

https://www.youtube.com/watch?v=s3KG4kn-ymY&ab_channel=Dynatrace (example of how it works)