Floss: address clock drift in asrc

Since ISO packets are sent out at fixed intervals, the |RepeatingTimer|
utility determines an important time domain.

By default, it uses NTP-adjusted clocks, the difference between the
timestamps of which is compatible with
|CLOCK_REALTIME/MONOTONIC/BOOTTIME| and such, aligning with Android's
audio server.

However, CrAS uses |CLOCK_MONOTONIC_RAW|, which is another time domain,
unaffected by NTP, and this can cause xruns when the clock drift
accumulates, which does relatively quickly.

This CL adds a parameter to |RepeatingTimer| to allow scheduling based
on |CLOCK_MONOTONIC_RAW|, where despite each |DelayedCallback| can still
drift (since libchrome schedulers use NTP-adjusted clocks), in the long
run they are aligned.

Bug: 333334341
Test: m Bluetooth
Flag: EXEMPT floss only changes

Change-Id: Ie90952138d53a67171f526db55edd604306a96f6