Bring better performances

[theofidry]

• Remove the deprecated Humbug\PhpScoper\Console\Configuration and make the parent Humbug\PhpScoper\Configuration final
• Replace usage of uniqid by bin2hex(random_bytes())
• Move namespace related PhpParser classes under PhpParser\NamespaceStmt
• Similar change as namespaces for use statements
• Introduce NamespaceManipulator and UseStmtManipulator in order to add the original name of the statement as an attribute and leverage this instead of (deep) cloning the whole node; this avoid to have to rely on heavy serialize/unserialize calls
• Heavily simplify the Reflector class by leveraging the phpstorm stub maps (which is generated by BetterReflection at the moment) instead of requiring to retrieve the whole reflection class for a given symbol

Closes #321