Run functional tests on azure pipelines

[ki4070ma]

The problem

Although python-client has functional tests, those don't run on ci.
If functional tests run with the latest appium periodically, we can find breaking environment
between python-client and appium in early.
(Running on every PR is too much from running time point of view. Enough nightly?)

[ki4070ma]

Task

• iOS
  • Run tests on azure pipelines in parallel
  • Publish test reports
• Android
  • Run tests on azure pipelines in parallel
  • Take screenrecord (to know what's happened)
  • Resolve flaky tests
  • Resolve flaky tests(touch_action, multi_action, find_by_accessibility_id, find_by_uiautomator)
• Common
  • Run also on appium beta ver
  • (Run appium server via Python script)
  • (Resolve below error if possible)

The agent: Azure Pipelines 5 lost communication with the server.
Verify the machine is running and has a healthy network connection.
For more information, see: https://go.microsoft.com/fwlink/?linkid=846610 

[ki4070ma]

Good example:

• Set up CI with Azure Pipelines java-client#1059
• https://github.com/appium/ruby_lib_core

[ki4070ma]

Will fix flaky tests by #472