* usermods only need to to `if (!pinManager.joinWire()) return;`
* joinWire will
* * check if global I2C are defined - return false if not defined
* * aloocate HW_I2C pins - return false on error
* * call Wire.begin() if needed.
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.
