Fix bogus port disconnection during serial event

[facchinm]

Fixes #9785 and probably many others

This commit strongly simplifies the serial list code

Pluggable discovery introduced a bug since BoardPort.toString() started reporting only the name of the port, not the complete name_vid_pid needed to match liblistserial output.
Adding .toCompleteString() almost solves the bogus disconnection part alone, but resolveDeviceByVendorIdProductId() uses "0x" prefixes VID/PID, breaking it again.

In addition, all the logic used to match a board with its bootloader (to obtain a serial number on 32u4 boards) has been completely removed since it is currently useless (and unused).

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[ArduinoBot]

✅ Build completed.

Please test this code using one of the following:

⬇️ https://downloads.arduino.cc/javaide/pull_requests/arduino-PR-9862-BUILD-929-linux32.tar.xz
⬇️ https://downloads.arduino.cc/javaide/pull_requests/arduino-PR-9862-BUILD-929-linux64.tar.xz
⬇️ https://downloads.arduino.cc/javaide/pull_requests/arduino-PR-9862-BUILD-929-windows.zip
⬇️ https://downloads.arduino.cc/javaide/pull_requests/arduino-PR-9862-BUILD-929-macosx.zip
⬇️ https://downloads.arduino.cc/javaide/pull_requests/arduino-PR-9862-BUILD-929-linuxarm.tar.xz

ℹ️ The linuxarm build is still experimental and may not be always available.

[matthijskooijman]

Fix and cleanups look good to me, thanks!

I wanted to test this, but could not reproduce the problem again with the setup I tried just now, so I might need to retest this when I get back to the office (not sure when that will be, though, so don't wait for that).