use Context instead of PolyglotContext

...gine/src/com/oracle/truffle/r/engine/shell/REmbedded.java

...her/src/com/oracle/truffle/r/launcher/ConsoleHandler.java

.../com/oracle/truffle/r/launcher/JLineConsoleCompleter.java

...rc/com/oracle/truffle/r/launcher/JLineConsoleHandler.java

....launcher/src/com/oracle/truffle/r/launcher/RCommand.java

...her/src/com/oracle/truffle/r/launcher/RscriptCommand.java

...src/com/oracle/truffle/r/runtime/context/ContextInfo.java

...ruffle/r/test/engine/shell/TestJLineConsoleCompleter.java

mx.fastr/suite.py