Experiment: Introduce TruffleString with higher level string functions

[antonykamp]

Background

We conducted an experiment, documented in #203, where we introduced TruffleStrings to TruffleSqueak. The takeaway was that the Squeak string operation primitives are too atomic to leverage the optimizations of TruffleStrings. Most of the time, we read and write bytes, but TruffleStrings are optimized for more complex operations.

Experiment

Experiment whether it's possible to

• use TruffleStrings as storage for ByteStrings, ByteArrays, ByteSymbols and WideStrings and
• introduce new primitives to higher string operations