Fix and refactor analog input class

[brentru]

This pull request:

• Resolves Feather HUZZAH ESP32 Pot. no data #406
• Refactors Wippersnapper_AnalogIO class:
  • Changes processAnalogInputs() to update() to match other, newer, component class APIs. Large refactoring for readability and maintainability around this new method
  • Added encodePinEvent func to encode and publish signal message to IO
  • Removes unused initAnalogOutputPin, superseded by PWM class
• Refactors configurePinRequest() into configAnalogInPinReq() and configureDigitalPinReq()
• Note: this is not a complete refactoring of the class, only what I was confused about/thought needed immediate attention for maintainability and compatibility with other component APIs.

Resolves:
#406
#403 (needs testing!)

Required tests prior to merging:

• Test LED component toggle (digital class since decoder func. was touched
• Test Pot. component: Periodic polling, raw adc
• Test Pot. component: Periodic polling, voltage
• Test Pot. component: "on change" polling, raw adc
• Test Pot. component: "on change" polling, voltage
• Test Pot. with PicoW