Always support commit-logging without performance penalty

Fast variant should only be used when logging is disabled

This incurs a negligible performance impact

Allow reads/writes to reserved CLINT regions

Previously, all loads/stores to reserved regions caused access faults.
Now, loads to reserved regions return 0, while writes are dropped.
This more closely matches actual hardware implementations

arith.h: remove redundant y1 = t; in mulhu(uint64_t, uint64_t)

local y1 is set to local t
y1 is never accessed in the lines that follow

Support using sim.h/processor.h as public interfaces

This step is to ensure that removing config.h out of headers will not cause regressions.

Add github actions test on macos

Fix build broken by #1170 and #1180

Print better error message when requesting >1024 harts