* use unsigned data types for counter values (#1151)
1. semantically it makes more sense
2. arithmetic over/underflow is not defined on signed ints, whereas it
is on unsigned ones, so this removes a potential source of bugs.
* #1151: fixup: PRI format
* #1151: fixup: return types
* #1151: fixup: wrap/indent
* fixup: arc_custom/micro_time.cc: no longer required to mask out top bit
Co-authored-by: Pauline Sho <psho@google.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>