FirstClassCallableRector should also change simple function names

[flack]

Feature Request

Currently, FirstClassCallableRector will transform this code:

-$result = array_map([$this, 'removeWhitespace'], $input);
+$result = array_map($this->removeWhitespace(...), $input);

It would be great if it could also transform this:

-$result = array_map('trim', $input);
+$result = array_map(trim(...), $input);

[samsonasik]

implemented at rectorphp/rector-src#6027

[nikolicaleksa]

@flack Please be aware that with the next release of Rector you will explicitly need to enable the first-class-callable rule for functions. See this issue and this PR