stm32/tinyusb: Add High-Speed USB support and fix CDC/VBUS issues.

[andrewleech]

Summary

The STM32 port's TinyUSB integration only worked on the FS controller. Boards with a HS controller (PYBD_SF6, STM32F429DISC, OLIMEX_H407, or ULPI-based designs) couldn't use TinyUSB at all — the RHPORT configuration was hardcoded to RHPORT 0 / full-speed only.

This branch adds proper RHPORT mode selection in tusb_config.h based on MICROPY_HW_USB_HS and MICROPY_HW_USB_HS_IN_FS board config, routes HS IRQ handlers to the correct RHPORT (including STM32N6 which maps HS to RHPORT 0), and adds VBUS sensing configuration for the HS-in-FS path on STM32F4/F7 (mirroring the existing FS path, with support for both VBDEN and legacy NOVBUSSENS register variants).

Also fixes two issues discovered during testing: a CDC reconnect stall caused by a stale endpoint halt left from a prior USB disconnect, and TX FIFO data from a previous connection blocking writes on reconnect. The DFU bootloader serial number now matches the ST algorithm so the device maintains a consistent identity across MicroPython and DFU modes. A TinyUSB-specific boot.py template is added to factoryreset.c.

Testing

Built with CFLAGS_EXTRA=-DMICROPY_HW_TINYUSB_STACK=1 for:

• PYBD_SF6 (F7, HS-in-FS) — flashed and verified CDC serial, machine.USBDevice API, filesystem access
• STM32F429DISC (F4, HS-in-FS) — build only
• OLIMEX_H407 (F4, HS-in-FS) — build only
• NUCLEO_H563ZI (H5, FS only) — build only, regression check

STM32N6 and ULPI boards were not tested on hardware (no boards available), verified by code inspection only.

Trade-offs and Alternatives

The RHPORT configuration uses #ifndef guards so boards like STM32N6 that pre-define CFG_TUSB_RHPORT0_MODE in mpconfigboard_common.h pass through unchanged. This avoids needing per-family #if chains but means any future HS-capable family (e.g. STM32U5) would need its own board-level override.

[github-actions]

Code size report:

Reference:  rp2/modules/rp2.py: Don't corrupt globals on asm_pio() exception. [c3ca843]
Comparison: stm32: Match ST DFU bootloader serial number in TinyUSB. [merge of 90b01a9]
  mpy-cross:    +0 +0.000% 
   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
      esp32:    +0 +0.000% ESP32_GENERIC
     mimxrt:   +48 +0.013% TEENSY40
        rp2:   +32 +0.003% RPI_PICO_W
       samd:   +28 +0.010% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:    +0 +0.000% VIRT_RV32