Robustness JMLC wrt non-thread-local prepare and execute

The JMLC API has an underlying assumption that prepared scripts are created and executed by the same thread because compiler configurations and output variable names for dynamic recompilation are maintained with thread-local variables. However, in complex scoring pipelines this is not the case leading to performance issues (e.g., multi-threaded operations despite single-threaded configuration) and in the worst case lost result variables.