pw_chrono_zephyr: Resolve multiple issues SystemTimerZephyr

Adds a new system_timer_test.cc file, which runs fine on the native
simulator target. The test adds basic coverage for the functionality of
the system_timer.cc file, and also covers some specific edge cases where
bugs here found and fixed.

- When 64 bit timeouts were configured, the implementation computed a
  `time_until_deadline` that was a negative value, and was not clamped,
  causing a wait forever.
- With 64 bit timeouts, kMaxTimeout effectively was -2, and
  that value passed as a timeout would either result in an error or no
  wait.
- Using K_TICK_MAX in deriving kMaxTimeout proved to be problematic with
  64 bit timeouts on Zephyr, as it turned out there was an overflow in
  the kernel leading to effectively K_NO_WAIT. The max needed a small
  adjustment.
- If InvokeAt() or InvokeAfter() was called a second time to reschedule
  the wake-up, the k_work_schedule() function did not do anything as the
  wake-up was already scheduled. The fix was to call k_work_reschedule()
  instead, as this both schedules a new wake-up, or reschedules it if
  already scheduled.
- If 32 bit timeouts are used, the compiler complained about a downcast
  from a long (chrono duration) to an int for the call into the Zephyr
  API. A static cast is added to eliminate the warning.

Bug: b:512561694
Bug: b:512561066
Test: "./pw build pw_smoke_tests" (under zephyr-bazel)
Change-Id: Idba728d56e1ca0f01d69c326ca5a4044252acd7d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/418432