I2SIn streaming protocol changes

[FoamyGuy]

Implements changes from feedback in #11064

• Remove wrapper functions for get and reset buffer
• Remove output_bit_depth property in favor of bits_per_sample that comes from the streaming interface
• Cleaned up docstrings, correct references to order and remove reference to internal var name.

The change to use self->base.sample_rate instead of self->sample_rate could work in the espressif port I think, but in raspberrypi port those values end up differing slightly. See comment and code link in 11064 for details. For now I've just left them alone for both so that the classes in the different ports are the same. I'm open to ideas on how best to handle it.

[tannewt]

Looks good to me! Thank you!