MKR WiFi 1010 - BQ24195L - OTG / 5V boost mode support

As per https://forum.arduino.cc/index.php?topic=588368.0 I've been working to try to get the BQ24195L into "boost" or "OTG" mode so it can supply 5V to the board.

The IC looks to support this via writing `10` to `REG01[5:4]` and the `OTG` pin being high.

However, writing the appropriate register value and trying to set the pin (to both `LOW` and `HIGH` via `digitalWrite(PIN_USB_HOST_ENABLE, ...)` doesn't change the board's 5V pin from 3.3V when only the battery is connected.

Other boards/cores have an `enableOTG()` somewhere in their libraries. I am very very keen indeed to get this functionality working. It seems like the board was designed with this in mind - can anyone advise? Can we get it in to the standard library for the board?

I created a Windows desktop tool and associated Arudino sketch here - https://github.com/kierenj/bq24195-mkr-wifi-debug/ - for debugging, but I can't get it to work :'(

I'd be eternally grateful for any assistance.

Start with the linked Arduino sketch and the BQ24195L behavior described for REG01[5:4], the OTG pin, and PIN_USB_HOST_ENABLE. Compare this with the board's standard library and other cores' enableOTG() entry points. Done means reliable OTG/boost operation supplies 5V from battery power and the support is available through the standard board library.

Written by the indexing model from the issue text.