Make ISimulatorTools private

Currently the ISimulatorTools used in the ISF are public tools in both jobs using the old style SimKernel and jobs using the MT-compatible SimKernelMT. This merge request makes the ToolHandleArray<ISimulatorTool> owned by SimKernelMT private. This has the side effect of changing the random number seeds used in these tools (as the seeding was based on the tool names). In order to mitigate this effect, the random number streams used by the tools are now seeded using a configurable stream name rather than the name of the tool.