Extend scope of Variable Library items to include Gen2 Dataflows and Deployment Pipelines

It would be great to extend the scope of Variable Library items to other fabric items. 2 use cases are:

• Expose library varaiables and assign them via stage rules / parameters in deployment pipelines.
• Ability to access library variables when authoring Gen2 git ci/cd Dataflows.

Extending the use of such "global variables" increases implementation flexability and does away with brittle workarounds.

NB At present it is not possible to select Deployment Pipelines Rules/Parameters for Gen2 git ci/cd Dataflows.