Some ports need an extra operation to ensure that the main task is
awoken so that a queued background task will execute during an ongoing
light sleep.
This removes the need to enable supervisor ticks while I2SOut is operating.
Closes: #3952
Originally, I believed the implementation might be shared with AudioOut,
as on the ESP32 (non-S2) the I2S peripheral was also used to drive the DAC.
However, this is not the case on ESP32-S2 and appears it will not be
the case with the ESP32-S3 or -C3, to the extent that there's skeletal
support for either of them in esp-idf master branch.
However, it could still be shared by I2SIn or PDMIn (the latter being
hypothetically implemented as I2SIn + digital postprocessing like we did
in the atmel-sam port, to my understanding), so I moved it to
the common-hal folder.
.. otherwise, the background callback to load the I2S fifos does not get
run. (I'm not sure this is _correct_ behavior of sleep + background
tasks, but it is the current behavior)
