[CodeQuality] FuncLikeToFirstClassCallableRector

[peterfox]

Changes

• Adds the FuncLikeToFirstClassCallableRector rule
• Adds tests for the new rule
• Added to the code quality set
• Changes applied by the rule itself to Rector's own code through being added to the set
  • src/Configuration/RectorConfigBuilder.php
  • src/Util/ArrayParametersMerger.php

Why

This reduces the user of Closures and Arrow functions where they are basically redundant and code be replaced by a First-Class Callable instead of being wrapped in a closure.

-function ($parameter) { return Call::to($parameter); }
+Call::to(...);

Notes

I debated what group this should be in. It could be considered Code Quality but equally it could be Deadcode or even Code Style. I'm happy to change it based on feedback.

Risk

There might be some risk for this if used with closure binding e.g.

$function = function ($foo) { return $this->foo($foo); };
$function->bindTo($obj);

Might end up as

$function = $this->foo(...);
$function->bindTo($obj);

If that's a problem then I can make the rule avoid method calls of $this.