frameworks/base: Vote to turn off io_is_busy during recording.

When recording starts, vote to turn off io_is_busy. After
recording stops, take out that vote so that io_is_busy can
go to its original value. Doing this saves power by reducing
the amount of time for which the CPU runs at high frequencies
when encoded data is being written to the SD card - a process
that causes io_wait times to shoot up. With io_is_busy turned off,
these wait times will not be considered as CPU busy time and so
the ondemand governor will not unnecessarily bump up the clock rate.
The votes are handled by the CpuGovernorService. Also move the
dynamic sampling rate and vote processor classes out of the
CpuGovernorService to improve modularity.