[Enhancement] Make ensure_ascii adjustable in ContainerEngineHandler #192

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Is your feature request related to a problem? Please describe.
Allow unicodes to show in log instead of ascii character (for example, show chinese word '哈' in log instead of something like '\u8bed')

Describe the solution you'd like
Add a constructor parameter json_ensure_ascii in class ContainerEngineHandler and add a parameter json_ensure_ascii in def format_stackdriver_json

Describe alternatives you've considered
Currently no...

Additional context
Nope