Test framework migration

**Is your feature request related to a problem? Please describe.**

As bussiness logic going more and more complex, we might overwrite/extend the our test framework Azure/azure-python-devtools more and more.

For now, we temporary decide to keep sharing the that repo between Azure SDK team and us. Because we found it's not necessary to split for now as human resource, degree of code dependency, convenience, etc.

Opening this issue to track the history we need to midify the test framework or overwrite/extend from our side. Maybe we might need to fork / reimpelement Azure CLI test framework someday as we need more dedicated features for Azure CLI like more leverage pytest, and bug fix, etc.

**Describe the solution you'd like**

**Describe alternatives you've considered**

**Additional context**