refactor(hal): Deprecate DevBoards class and bring HardwareSerial class up to the Sketch Layer

[ZZ-Cat]

Overview

This Pull Request deprecates the original DevBoards Hardware Abstraction Layer class and is replaced by Arduino's HardwareSerial class

Details

After a couple of failed attempts at trying to implement a system where you could pick your UART pins vicariously through simply picking which port you wanted, I have decided to bring the HardwareSerial class up to the Sketch Layer.
Here, this gives you more freedom to feed in your own hardware-specific UART port that you want CRSF for Arduino to use.

API Change

This introduces a change to CRSF for Arduino's API - Specifically to do with the constructor.
Instead of passing in the pins your receiver is connected to, you are passing in your chosen HardwareSerial class.

The old way

You would create an instance of CRSF for Arduino in the following ways:

/* As a fixed global instance - This is how Arduino shows most makers.*/
#include <CRSFforArduino.hpp>

#define SERIAL_RX_PIN 0
#define SERIAL_TX_PIN 1

/* This is how we used to do it. */
CRSFforArduino crsf = CRSFforArduino(SERIAL_RX_PIN, SERIAL_TX_PIN);

/* Allocated in dynamic memory (for the C++ Aficionados among us) */
#include <CRSFforArduino.hpp>
#include <new>
using namespace std;

#define SERIAL_RX_PIN 0
#define SERIAL_TX_PIN 1

CRSFforArduino *crsf = nullptr;

void setup()
{
    /* This is how we used to do it. */
    crsf = new CRSFforArduino(SERIAL_RX_PIN, SERIAL_TX_PIN);
}

The new way

Now, you create an instance of CRSF for Arduino in the following ways:

/* As a fixed global instance - This is how Arduino shows most makers.*/
#include <CRSFforArduino.hpp>


/* With your board's default UART port - Serial1: */
CRSFforArduino crsf = CRSFforArduino(&Serial1);

/* Allocated in dynamic memory (for the C++ Aficionados among us) */
#include <CRSFforArduino.hpp>
#include <new>
using namespace std;

CRSFforArduino *crsf = nullptr;

void setup()
{
    /* This is how we do it now. */
    crsf = new CRSFforArduino(&Serial1);
}