Updated Shray with newer features, including the state as used for the PPoPP24 submission

Added many extra features (e.g. thread-safety), reworked core library (removed prefetch, added GASNet interaction API), extended benchmarks.

Up to commit 386fc874 was used for the benchmarks in the PPoPP'24 submission. The other commits only do some renaming of preprocessor macro's, as well as work on a pure Makefile build system. Finally, the proper license information was added.