Create tests for func pack

[aishwaryabh]

Create tests for creating a function app in each runtime and then running func pack to make sure that it zips up in the intended output directory. This would ensure that func pack is in a good state today and catch any regressions (if any). We also want to isolate any stack specific logic and make this extensible.

The steps that would need to run in the test are the following:

• Create a function app in specified runtime
• Attempt to run func pack and check if zip was created in correct output directory
• [Stretch goal] Run an Az CLI deployment at the end of the test to test if pack command executed correctly

Also create tests for the scenario where we have a .funcignore specified