feat: Blues Heron (STM32U575CIT6)

[zfields]

In draft PR state, until CDC issue is resolved.

Failing in premain() at:

premain()
└─ init()
   └─ hw_config_init()
      └─ USBD_CDC_init()
         └─ CDC_init()
            └─ USBD_Init()
               └─ USBD_LL_Init()
                  └─ HAL_PCD_Init()
                     └─ USB_CoreInit()
                        └─ USB_CoreReset()

It only seems to exit the following loop with HAL_TIMEOUT:

  /* Core Soft Reset */
  USBx->GRSTCTL |= USB_OTG_GRSTCTL_CSRST;

  do
  {
    count++;

    if (count > HAL_USB_TIMEOUT)
    {
      return HAL_TIMEOUT;
    }
  } while ((USBx->GRSTCTL & USB_OTG_GRSTCTL_CSRST) == USB_OTG_GRSTCTL_CSRST);

  return HAL_OK;
}

Since I never make it into initVariant(), I'm not sure how I'm supposed to adapt my implementation.

There appears to be a related issue #2855. Currently awaiting response to my request for clarification.