[Maybe] Do not use the ugly regex, i.e: abandon this package

[tangrufus]

Modify https://github.com/Roave/FunctionFQNReplacer to perform search and replace.

Main difference: https://github.com/Roave/FunctionFQNReplacer/blob/master/src/NodeVisitor/ReplaceUnqualifiedFunctionCallsWithQualifiedReferences.php#L123-L137

[tangrufus]

Or, make a composer plugin for https://github.com/humbug/php-scoper

Multiple users moved away from imposter to php-scoper.
See:

• Almost the last part of a modern WordPress development #149
• Issues with Guzzle (PSR4 transforming) imposter-plugin#39