[Core] Add Raspberry Pi RP2040 support (#14877)

* Disable RESET keycode because of naming conflicts

* Add Pico SDK as submodule

* Add RP2040 build support to QMK

* Adjust USB endpoint structs for RP2040

* Add RP2040 bootloader and double-tap reset routine

* Add generic and pro micro RP2040 boards

* Add RP2040 onekey keyboard

* Add WS2812 PIO DMA enabled driver and documentation

Supports regular and open-drain output configuration. RP2040 GPIOs are
sadly not 5V tolerant, so this is a bit use-less or needs extra hardware
or you take the risk to fry your hardware.

* Adjust SIO Driver for RP2040

* Adjust I2C Driver for RP2040

* Adjust SPI Driver for RP2040

* Add PIO serial driver and documentation

* Add general RP2040 documentation

* Apply suggestions from code review

Co-authored-by: Nick Brassel <nick@tzarc.org>

Co-authored-by: Nick Brassel <nick@tzarc.org>

platforms/chibios/boards/GENERIC_PROMICRO_RP2040/configs/config.h

@@ -0,0 +1,62 @@
+// Copyright 2022 Stefan Kerkmann
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+/**======================
+ **    I2C Driver
+ *========================**/
+
+#if !defined(I2C_DRIVER)
+#    define I2C_DRIVER I2CD2
+#endif
+
+#if !defined(I2C1_SDA_PIN)
+#    define I2C1_SDA_PIN GP2
+#endif
+
+#if !defined(I2C1_SCL_PIN)
+#    define I2C1_SCL_PIN GP3
+#endif
+
+/**======================
+ **    SPI Driver
+ *========================**/
+
+#if !defined(SPI_DRIVER)
+#    define SPI_DRIVER SPID0
+#endif
+
+#if !defined(SPI_SCK_PIN)
+#    define SPI_SCK_PIN GP18
+#endif
+
+#if !defined(SPI_MISO_PIN)
+#    define SPI_MISO_PIN GP20
+#endif
+
+#if !defined(SPI_MOSI_PIN)
+#    define SPI_MOSI_PIN GP19
+#endif
+
+/**======================
+ **      SERIAL Driver
+ *========================**/
+
+#if !defined(SERIAL_USART_DRIVER)
+#    define SERIAL_USART_DRIVER SIOD0
+#endif
+
+#if !defined(SERIAL_USART_TX_PIN) && !defined(SOFT_SERIAL_PIN)
+#    define SERIAL_USART_TX_PIN GP0
+#endif
+
+#if !defined(SERIAL_USART_RX_PIN)
+#    define SERIAL_USART_RX_PIN GP1
+#endif
+
+/**======================
+ **    Double-tap
+ *========================**/
+
+#define RP2040_BOOTLOADER_DOUBLE_TAP_RESET