Pull Through Caching from Another Azure Container Registry

**What is the problem you're trying to solve**
The proposed feature aims to enhance the efficiency and reliability of Azure Container Registry (ACR) by supporting Azure Container Registry as a upstream in the already existing [Pull Through Caching functionality](https://learn.microsoft.com/en-us/azure/container-registry/tutorial-artifact-cache). This feature enables a production ACR to pull specific artifacts from a development ACR, streamlining the deployment process and ensuring high availability of essential images while optimizing storage utilization.

In many development scenarios, organizations maintain separate Azure Container Registries for development and production environments. However, the development ACR often accumulates numerous artifacts, including those unnecessary for production deployment. This results in increased storage costs and management overhead. Moreover, the lack of High Availability (HA) in development ACRs can pose challenges during critical deployments.

**Describe the solution you'd like**
Introduce Azure Container Registry as a upstream in the Pull Through Caching functionality in Azure Container Registry. This will enable the production ACR to selectively fetch artifacts from the development ACR. This allows organizations to leverage the vast repository of artifacts in the development ACR without compromising on production performance or availability.

**Additional context**
The introduction of Pull Through Caching from another Azure Container Registry represents a significant enhancement to the Azure Container Registry ecosystem. By enabling selective artifact pulling, automatic synchronization, and enhanced reliability, this feature empowers organizations to optimize costs, streamline deployment processes, and simplify ACR management tasks.