drivers: add driver for IS31FL3731 matrix LED driver

[antonfisher]

This PR adds a driver for IS31FL3731 matrix LED driver. Datasheet: https://www.lumissil.com/assets/pdf/core/IS31FL3731_DS.pdf The first version is basic, but functional.

What's implemented:

• picture mode ("auto frame play mode" and "audio frame play mode" are not supported in this version of the driver)
• drawing by XY coordinates or raw pixel's index on LED layout
• frames (0-7) and switching between them.

Supported boards:

• any custom LED matrix layout built on IS31FL3731 -- using DrawPixelIndex(...) function
• Adafruit 15x7 CharliePlex LED Matrix FeatherWing (CharlieWing) -- using DrawPixelXY(...) or DrawPixelIndex(...) function (I've tested on this one with NRF52840 controller).

Boards can be added in the future versions:

• Adafruit 16x9 Charlieplexed PWM LED Matrix Driver - IS31FL3731 -- I've ordered it, waiting to test.

Tests:

• fmt-check pass
• unit-test pass
• smoke-test pass for the driver: Except the AVR part fails because I do not have avr-gcc installed.

Example code works like this:

[deadprogram]

Thank you @antonfisher for working on this, and thanks @ysoldak for proving all of the feedback/reviews.

I am going to squash/merge now.