[GR-6518] Fix deparsing of transitive varargs (e.g. "..1").

...e.r.nodes/src/com/oracle/truffle/r/nodes/RASTBuilder.java

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

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

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

...fle.r.runtime/src/com/oracle/truffle/r/runtime/Utils.java

...src/com/oracle/truffle/r/runtime/nodes/RSyntaxLookup.java

...est/src/com/oracle/truffle/r/test/ExpectedTestOutput.test

...racle/truffle/r/test/builtins/TestBuiltin_substitute.java