Allow parsing non-Unicode nginx configurations

[defanator]

Proposed changes

This PR allows crossplane to parse non-Unicode nginx configurations without throwing UnicodeDecodeError. Such configurations are considered valid by nginx itself, so there is no reason for crossplane to give up on that.

The replace error handler was chosen as it allows to quickly determine whether there were any non-UTF symbols in the input by looking for the replacement sequence in parsed contents:
https://docs.python.org/3/library/codecs.html#error-handlers

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto master
• I will ensure my PR is targeting the master branch and pulling from my branch from my own fork