allow pulling azure cli docker image from artifactory

We are not able to use az-cli action from self hosted runners because connection to mcr.microsoft.com not open from our firewall. Could you please update the action to read image path from environment variable where we can provide on-prem artifactory remote repository?

```
Warning: Unable to fetch all az cli versions, please report it as an issue on https://github.com/Azure/CLI/issues. Output: , Error: Error: The process 'curl' failed with exit code 35
Starting script execution via docker image mcr.microsoft.com/azure-cli:2.30.0
Error: Error: Unable to find image 'mcr.microsoft.com/azure-cli:2.30.0' locally
docker: Error response from daemon: Get "https://mcr.microsoft.com/v2/": EOF.
```

**Reference** : Similar feature is implemented in https://github.com/marketplace/actions/setup-jfrog-cli#downloading-jfrog-cli-from-artifactory.