* Make zombienet tests native friendly

* Update zombienet_tests/README.md

Co-authored-by: Bastian Köcher <info@kchr.de>

* Get rid of `{{ZOMBIENET_NATIVE_BINARY_PREFIX}}`

* Remove pointless changes

* add set_env helper and doc in readme

* changes from feedback

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Co-authored-by: Bastian Köcher <info@kchr.de>
Co-authored-by: Javier Viola <javier@parity.io>