reflection: Fix the return value of ReflectionFunction::{getNamespaceName,inNamespace}() for closures (#16129)

* reflection: Fix the return value of ReflectionFunction::{getNamespaceName,inN

reflection: Fix the return value of ReflectionFunction::{getNamespaceName,inNamespace}() for closures (#16129)

* reflection: Fix the return value of ReflectionFunction::{getNamespaceName,inNamespace}() for closures

Fixes GH-16122

* reflection: Clean up implementation of `ReflectionFunctionAbstract::inNamespace()`

* reflection: Clean up implementation of `ReflectionFunctionAbstract::getNamespaceName()`

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reflection: Fix ReflectionFunction::getShortName() for first class callables (#14087)

Fix fixes an incorrect fix in php/php-src#14001.