fix: Multiple gRPC `Create/Init/Destroy` cycles causes multiple plugg…

…able-discovery zombie process (arduino#2985)

* Refactor mocked-discovery integration tests

* Added integration-test to check handling of multiple discovery instances

* Correctly clean-up pluggable-discoveries on gRPC instance close

Move the "debian package" copyright file into the correct folder (ard…

…uino#2955)

* Move the copyright file into the correct folder

* Fix the location of the copyright file

* fix debian in correct location

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Co-authored-by: Alessio Perugini <alessio@perugini.xyz>

Fixed release workflow build

[skip-changelog] Investigate some integration-test failures (increase…

… debugging prints) (arduino#2844)

[skip changelog] Renamed FQBN.Packager -> FQBN.Vendor (arduino#2836)