simplify and unify group generics implementation

...fle.r.nodes/src/com/oracle/truffle/r/nodes/RASTUtils.java

...nodes/src/com/oracle/truffle/r/nodes/RTruffleVisitor.java

...com/oracle/truffle/r/nodes/access/AccessArgumentNode.java

...fle/r/nodes/access/array/write/UpdateArrayHelperNode.java

...rc/com/oracle/truffle/r/nodes/function/ArgumentsNode.java

.../truffle/r/nodes/function/BinaryOpsGroupDispatchNode.java

...src/com/oracle/truffle/r/nodes/function/DispatchNode.java

...m/oracle/truffle/r/nodes/function/DispatchedCallNode.java

...racle/truffle/r/nodes/function/GroupDispatchCallNode.java

...om/oracle/truffle/r/nodes/function/GroupDispatchNode.java

...acle/truffle/r/nodes/function/NextMethodDispatchNode.java

...c/com/oracle/truffle/r/nodes/function/S3DispatchNode.java

...e/truffle/r/nodes/function/UnaryOpsGroupDispatchNode.java

...racle/truffle/r/nodes/function/UseMethodDispatchNode.java

...s/src/com/oracle/truffle/r/nodes/runtime/RASTDeparse.java

...rc/com/oracle/truffle/r/nodes/runtime/RASTHelperImpl.java

....runtime/src/com/oracle/truffle/r/runtime/RArguments.java

...le.r.runtime/src/com/oracle/truffle/r/runtime/RError.java

...time/src/com/oracle/truffle/r/runtime/RGroupGenerics.java