[MESH] - Add eRPC functionality to IAR examples

Since ex_gen did not support mixed C/C++ projects for IAR, eRPC (c++ based module) could not be supported by the original IAR mesh examples.
As a consequence, the IAR mesh examples were split from the main mesh examples: for example, you would find both: "simple_mesh_node" example and "simple_mesh_node_iar" example projects, where the "simple_mesh_node" would contain the mesh example with eRPC ability and the "simple_mesh_node_iar" example would contain only the mesh example without support for eRPC.

Since swtools have added (by default) the support for IAR C/C++ mixed projects, the solution described above is irrelevant.

The following steps were made to enable eRPC with IAR mesh examples:

• Update swtools_version to 49.0.0.4
• Remove special "simple_mesh_node*_iar" examples.
• Add IAR toolchain for all simple_mesh_node examples.
• Since software tools upgraded, the following modifications were made:
  • Manually setting IAR examples optimization level to High - Size
  • Removing patch set specially for persistent_app in run_Xgen.sh