native_sim: Update native simulator to latest and align with it

Align with the latest upstream native simulator
4c595794588f9d7f67fcf0fe05c3db02892a00f9
including:

* 4c59579 Makefile: Add option to build native part
* 910f934 Makefile: NSI_EXTRA_INCLUDES option and lots of commentary
* d9bf489 cmd line parsin: Minor header refactoring
* 02f3555 cmd line cleanup: Run as NSI_TASK instead of calling expl.
* 2c88173 Split exit call in two
* 2b989b4 CPU IF change: nsif_cpu0_cleanup() to return int
* e696228 HW scheduler: Add API to get next event time
* ae0e9e8 native irq ctrl: Miscellaneous fixes and improvements
* 3fd84cd NSI_TASK: Add compile check of valid priority
* 7e09fb8 HW events: Change internal storage

And two minor updates to the native_sim board,
to align with this updated version:
* nsif_cpu0_cleanup(void) now must return an int
* We need to explicitly tell the native simulator build we want
  the native components built

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>