Change USBSerial.h constructor to allow to label the stream for, eg., redirecting stdin/out/err to a USBSerial object. Will not break existing default use as tested with mbed-os 5.11.5

Dependents:   max32630fthr_stdout2usb_mbed_v5-11-5 firmware_framework1

USBMSD/shortlog@6ef9c5c0250e: not found in manifest