tools: allow longer time periods

tools: allow longer time periods

We currently store time as microseconds in 32-bit integers and allow
seconds as the longest time unit when parsing command-line arguments
limiting the time period possible to specify when passing arguments such
as --hold-period to 35 minutes. Let's use 64-bit integers to vastly
increase that.

Use nanosleep() instead of usleep() to extend the possible sleep time
range.

Reported-by: Gunnar Thörnqvist <gunnar@igl.se>
Link: https://lore.kernel.org/r/20240423100452.32958-4-brgl@bgdev.pl
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>