tools: work around usbser.sys bug in idf_monitor
tools: work around usbser.sys bug in idf_monitor

implemented workaround in idf_monitor for known usbser.sys bug which
causes changes in RTS signal to only be sent if DTR signal also changes.
Works by forcing a dummy change in DTR signal (re-assigning its current
value, as it has previously been done in the flashing tool)

Closes https://github.com/espressif/esp-idf/pull/4676

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf