Improve co-existence of usermods sharing I2C

Improve co-existence of several popular usermods with respect to shared I2C bus.
- ensure that i2c_sda and i2c_scl are used when defined
- ensure that HW_PIN_SDA / HW_PIN_SCL are not overwritten
- ensure that Wire.begin()nis always called with user-defined pins (remove rogue Wire.begin() without parameters)
- ensure that set.cpp / cfg.cpp use esp32-specific global Wire objects.

wled00/set.cpp

@@ -1,3 +1,6 @@
+#include <Arduino.h>              // WLEDMM: make sure that I2C drivers have the "right" Wire Object
+#include <Wire.h>
+
 #include "wled.h"
 
 /*