Bugfix: google-play get-latest-build-number crashes on incomplete response

[priitlatt]

This fixes #208.

Action google-play get-latest-build-number uses Google Play Developer API method edits.tracks.get to obtain the latest build build number in certain release track.
While API documentation indicates that the response for Track resource should contain a list of Release objects that all have reference to CountryTargeting which has a field called includeRestOfWorld, in reality the includeRestOfWorld field might not be defined. This will result in the following error on client side:

Traceback (most recent call last):
  File "/home/docker/.local/lib/python3.8/site-packages/codemagic/cli/cli_app.py", line 200, in invoke_cli
    CliApp._running_app._invoke_action(args)
  File "/home/docker/.local/lib/python3.8/site-packages/codemagic/cli/cli_app.py", line 156, in _invoke_action
    return cli_action(**action_args)
  File "/home/docker/.local/lib/python3.8/site-packages/codemagic/cli/cli_app.py", line 412, in wrapper
    return func(*args, **kwargs)
  File "/home/docker/.local/lib/python3.8/site-packages/codemagic/tools/google_play.py", line 143, in get_latest_build_number
    track = self.api_client.get_track_information(edit.id, track_name)
  File "/home/docker/.local/lib/python3.8/site-packages/codemagic/google_play/api_client.py", line 92, in get_track_information
    resource = Track(**track_response)
  File "<string>", line 5, in __init__
  File "/home/docker/.local/lib/python3.8/site-packages/codemagic/google_play/resources/track.py", line 74, in __post_init__
    self.releases = [Release(**release) for release in self.releases]
  File "/home/docker/.local/lib/python3.8/site-packages/codemagic/google_play/resources/track.py", line 74, in <listcomp>
    self.releases = [Release(**release) for release in self.releases]
  File "<string>", line 10, in __init__
  File "/home/docker/.local/lib/python3.8/site-packages/codemagic/google_play/resources/track.py", line 59, in __post_init__
    self.countryTargeting = CountryTargeting(**self.countryTargeting)
TypeError: __init__() missing 1 required positional argument: 'includeRestOfWorld'```

In order to tackle the cases when includeRestOfWorld is not defined, make it optional field for CountryTargeting resource and set default value for it to None.

Affected actions:

• google-play get-latest-build-number.

[priitlatt]

This is the gist of the fix.