esp32s2: port_get_raw_ticks: Use a more efficient, monotonic routine
esp32s2: port_get_raw_ticks: Use a more efficient, monotonic routine

While trying to debug #3572, I noticed that I would frequently break in
the midst of gettimeofday and that the routine get_adjusted_boot_time
had to take and release locks.  Furthermore, we don't want "adjusted"
boot time, which could go forwards or backwards depending on the
adjustment (such as setting the clock used by gettimeofday() to the network
time)

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