ESP32-S2: Add PulseOut and PulseIn

[hierophect]

This PR adds the PulseOut and PulseIn IR transmission and reception modules to the ESP32-S2 port. Unlike other ports, which transmit pulse trains using timers and PWMOut carrier objects, the ESP32-S2 has a dedicated pulse train peripheral, the "RMT", which is capable of both sending and receiving pulses with and without carrier modulation.

Because of this, PulseOut does not require a PWMOut object, which uses an entirely different peripheral, the LEDC PWM controller. Thus, the API for PulseOut has been expanded to allow the ESP32 to receive a pin object, frequency and duty cycle in place of a PWMOut object. Other ports have been correspondingly internally updated for the change, but should see no difference in their python calls for the time being.

PulseIn has a couple of quirks that should be noted when reviewing.

• The RMT does not acknowledge or store any detected pulses until a certain "idle period" of no activity is met. I've set this to 90ms, which seemed like a practical value, but it does mean that long pulse trains with no breaks at all will not be acknowledged by the ESP32 - I'm not sure if this is an issue.
• The internal timing and storage of the RMT required that I slow the clock down by 3x in order to accommodate pulses of 65ms, which are common in the module's examples on ReadTheDocs and Learn. Pulses are thus delivered as smaller numbers from the RMT internally, and then multiplied by 3x before being returned.
• The RMT has no real sense of "idle state", using the idle period threshold to detect the start of a pulse train. I've set this by using pullups so the trigger pulse is meaningful, but I'm not sure if more work needs to be done there.

The RMT is shared by the Neopixel Write system. A mediator system in Peripherals reserves RMT channels individually. Up to 4 channels are available on any pin, so you can have a combination of 4 total PulseOut, PulseIn, and Neopixel lines active at any given time.

Tested on the ESP32-S2 Saola1 Wrover. Resolves #3264

[tannewt]

Thanks for adding this! Just a few corner cases to think about.

[tannewt]

One thing to make the builds pass and then should be good. Thanks!

[hierophect]

@tannewt I think this should be good to go.

[tannewt]

Thank you! Looks great.