Support "azure storage account connection-string show".

1. Support "azure storage account connection-string show".
2. Add a new script to run the unit test for Azure storage related cases.
This is fine if you want a separate command for your own purposes, but add the storage tests to the main testlist.txt file as well. The CI runs testlist.txt, and if your tests aren't in there they won't get run. This PR didn't run your tests, for example.