Added codecov token in cleartext

[cmaglie]

See: #36 (review)

The Codecov upload token will be no longer optional in v4 of the action, so it will be necessary to adjust the workflow to provide the token to the action at the same time as the bump. Doing so is a good idea anyway because, although supported in v3, the lack of a token was causing periodic spurious coverage data upload failures. That was done already in the Arduino CLI repo (arduino/arduino-cli#2129) and the approach used there has passed the test of time with flying colors.

The workflow does currently use the token input of the action, but it uses the flawed approach of storing it in a secret, which would cause the workflow run to fail on any PR submitted from a fork after the action bump. So the workflow must be updated to use the system implemented in the Arduino CLI workflow.

[cmaglie]

@per1234 @arduino/team_tooling
do you know a way to perform the var comparison in both Windows and UNIX runners?

Run if [[ "arduino/pluggable-discovery-protocol-handler" == "arduino/pluggable-discovery-protocol-handler" ]]; then
ParserError: D:\a\_temp\43fdaab8-e175-4fc8-9ad9-7a3b4bb08100.ps1:2
Line |
   2 |  if [[ "arduino/pluggable-discovery-protocol-handler" == "arduino/plug …
     |    ~
     | Missing '(' after 'if' in if statement.

Error: Process completed with exit code 1.

https://github.com/arduino/pluggable-discovery-protocol-handler/actions/runs/7098847869/job/19321628795?pr=40

[umbynos]

What about using conditional statement inside github actions?