Bugfix: decoding undefined byte sequences in process streams

[priitlatt]

In case there are byte sequences in the invoked subprocess output that do not have unicode representation, then unexpected UnicodeDecodeErrors might occur while decoding those byte chunks. An example stacktrace is as follows:

Traceback (most recent call last):
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/tools/_app_store_connect/actions/publish_action.py", line 88, in publish
    self._publish_application_package(altool, application_package, validate_package)
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/tools/_app_store_connect/actions/publish_action.py", line 116, in _publish_application_package
    self._validate_artifact_with_altool(altool, application_package.path)
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/tools/_app_store_connect/actions/publish_action.py", line 248, in _validate_artifact_with_altool
    result = altool.validate_app(artifact_path)
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/models/altool/altool.py", line 124, in validate_app
    return self._run_command(cmd, f'Failed to validate archive at "{artifact_path}"')
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/models/altool/altool.py", line 143, in _run_command
    stderr=subprocess.STDOUT,
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/cli/cli_app.py", line 430, in execute
    ).execute(**execute_kwargs)
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/cli/cli_process.py", line 92, in execute
    self._handle_streams(self._buffer_size)
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/cli/cli_process.py", line 72, in _handle_streams
    self._stdout += self._stdout_stream.process_buffer(buffer_size, self._print_streams)
  File "/Users/priit/.virtualenvs/cli-tools-shZ38mB-/lib/python3.7/site-packages/codemagic_cli_tools-0.9.1-py3.7.egg/codemagic/cli/cli_process_stream.py", line 58, in process_buffer
    chunk = bytes_chunk.decode(encoding='utf-8')
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe0 in position 8191: unexpected end of data

Result of this error is that the action execution will fail with unexpected error.