[skip changelog] Document full hardware requirements and effects of running integration tests (#785)

* Document full hardware requirements and effects of running integration tests

Previously, the full hardware requirements of the integration tests were not documented and no mention was made of what the tests do to all hardware meeting those requirements.

* Update docs re: Python version for integration tests

Co-authored-by: Roberto Sora <r.sora@arduino.cc>

Co-authored-by: Roberto Sora <r.sora@arduino.cc>

Author: per1234

docs/CONTRIBUTING.md

@@ -40,8 +40,8 @@ available in your local environment:
 
 If you want to run integration tests you will also need:
 
-* A serial port with an Arduino device attached
-* A working [Python][3] environment, version 3.5 or later
+* A serial port with an Arduino board attached
+* A working [Python][3] environment, version 3.8 or later
 
 If you're working on the gRPC interface you will also have to:
 
@@ -115,8 +115,21 @@ For these reasons, in addition to regular unit tests the project has a suite of
 integration tests that actually run Arduino CLI in a different process and
 assess the options are correctly understood and the output is what we expect.
 
-To run the full suite of integration tests you need an Arduino device attached
-to a serial port and a working Python environment. Chances are that you already
+#### Hardware requirements for running the full suite of integration tests:
+
+An Arduino board attached to a serial port. The board must:
+
+* Use one of the VID/PID pairs used by Arduino or their partners (as is the case
+with all modern official Arduino boards except the classic Nano).
+* Accept uploads using the FQBN associated with that VID/PID (which will be the
+case unless you have installed a custom bootloader or removed the bootloader).
+
+Note that running the integration tests will result in a sketch being uploaded
+to every attached Arduino board meeting the above requirements.
+
+#### Software requirements for running integration tests:
+
+A working Python environment. Chances are that you already
 have Python installed in your system, if this is not the case you can
 [download][3] the official distribution or use the package manager provided by
 your Operating System.