[GR-2527] Refactor UpCallsRFFI world.

...e/truffle/r/engine/interop/RForeignAccessFactoryImpl.java

.../engine/interop/ffi/llvm/TruffleLLVM_UpCallsRFFIImpl.java

com.oracle.truffle.r.native/fficall/src/jni/Rinternals.c

...src/com/oracle/truffle/r/nodes/ffi/FFIUpCallRootNode.java

...c/com/oracle/truffle/r/nodes/ffi/JavaUpCallsRFFIImpl.java

.../src/com/oracle/truffle/r/nodes/ffi/RFFIUpCallMethod.java

...c/com/oracle/truffle/r/nodes/ffi/TraceUpCallsAdapter.java

...odes/src/com/oracle/truffle/r/nodes/ffi/UpCallsIndex.java

...s/src/com/oracle/truffle/r/nodes/ffi/UpCallsRFFIImpl.java

...fi/src/com/oracle/truffle/r/runtime/ffi/jni/JNI_Call.java

...ime/src/com/oracle/truffle/r/runtime/ffi/RFFICstring.java

.../src/com/oracle/truffle/r/runtime/ffi/StdUpCallsRFFI.java

...oracle/truffle/r/test/tools/RFFIUpCallMethodGenerate.java