MPR121 Touch IC Based Keypad Input Module (#5103)

Implements an input driver utilising the MPR121 Touch IC and is compatible with common MPR121 keypad PCB's.

- Implements a "candybar" phone style 12-key keypad
  - multiple taps to rotate through the character set
  - longpress for navigation keys
  - keymap to allow arbitrary routing of MPR121 pin to button configuration
  - extendable to other key functions
- Integrates with the existing kbI2cBase implementation
- Works with CannedMessageModule Freetext mode
- Can be used with common MPR121 boards, such as https://www.amazon.com/MPR121-Capacitive-Keyboard-Buttons-Sensitive/dp/B083R89CHB/ref=sr_1_6
- Of use for PCB based radios, where some form of low surface area low component freetext input is required, but also without consuming too many IO pins.
- Tested on a T3S3 connected to Wire1 (Second) interface.
  - Demonstration of functionality: https://youtu.be/UI6QP6nGvhY

src/input/cardKbI2cImpl.cpp

@@ -12,8 +12,8 @@ void CardKbI2cImpl::init()
 #if !MESHTASTIC_EXCLUDE_I2C && !defined(ARCH_PORTDUINO)
     if (cardkb_found.address == 0x00) {
         LOG_DEBUG("Rescanning for I2C keyboard");
-        uint8_t i2caddr_scan[] = {CARDKB_ADDR, TDECK_KB_ADDR, BBQ10_KB_ADDR};
-        uint8_t i2caddr_asize = 3;
+        uint8_t i2caddr_scan[] = {CARDKB_ADDR, TDECK_KB_ADDR, BBQ10_KB_ADDR, MPR121_KB_ADDR};
+        uint8_t i2caddr_asize = 4;
         auto i2cScanner = std::unique_ptr<ScanI2CTwoWire>(new ScanI2CTwoWire());
 
 #if WIRE_INTERFACES_COUNT == 2
@@ -39,12 +39,17 @@ void CardKbI2cImpl::init()
                 // assign an arbitrary value to distinguish from other models
                 kb_model = 0x11;
                 break;
+            case ScanI2C::DeviceType::MPR121KB:
+                // assign an arbitrary value to distinguish from other models
+                kb_model = 0x37;
+                break;
             default:
                 // use this as default since it's also just zero
                 LOG_WARN("kb_info.type is unknown(0x%02x), setting kb_model=0x00", kb_info.type);
                 kb_model = 0x00;
             }
         }
+        LOG_DEBUG("Keyboard Type: 0x%02x Model: 0x%02x Address: 0x%02x\n", kb_info.type, kb_model, cardkb_found.address);
         if (cardkb_found.address == 0x00) {
             disable();
             return;