Fix a completely wrong calculation in mach monotime_init_internal()
Bug 1: We were purporting to calculate milliseconds per tick, when we should have been computing ticks per millisecond.
Bug 2: Instead of computing either one of those, we were actually computing femtoseconds per tick.
These two bugs covered for one another on x86 hardware, where 1 tick == 1 nanosecond. But on M1 OSX, 1 tick is about 41 nanoseconds, causing surprising results.
Fixes #40684 (closed); bugfix on 0.3.3.1-alpha.
We should backport this one, especially if it affects iOS too.