XiangShan-2 (NANHU) with DFT and SoC enhancements

This is the second generation of XiangShan (NANHU)
with some DFT and SoC enhancements.

* SCAN, shared bus MBIST support
* Update memory map for larger physical address space
* Fix real-time clock for CLINT
* Add support for external reset vector
* Other fixes and enhancements

The second generation of XiangShan (NANHU)

Add MulanPSL-2.0 License (OpenXiangShan#825)

emu: break on assertion failures after eval