Fix SymfonyFilter to filter class and method on tag @api

I have changed the tags' regexp to accept @api everywhere in the comment block.

I have changed the NodeVisitor to construct the class or the method before applying the filter because in the filter I need to know if the @api is present in comment.

I have changed the parser to handle the case where the class is rejected.

Finally I have changed the SymfonyFilter to use existing methods.