gRPC: if an Upload request is canceled, immediately terminate the upload tool process.

[cmaglie]

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What kind of change does this PR introduce?

If an Upload gRPC request is canceled, the underlying upload tool is terminated immediately.
In particular, this affects the Arduino IDE "cancel" button, because the IDE can only cancel the Upload gRPC request and has no control over the underlying upload tool.

What is the current behavior?

If an Upload gRPC request is canceled, the underlying upload tool is NOT terminated, and it may take a very long time to timeout and close itself.

What is the new behavior?

The upload tool is terminated immediately.

Does this PR introduce a breaking change, and is titled accordingly?

Other information

Related to:

• Canceling compilation or upload doesn't kill tool process arduino-ide#2517
• Allow user to terminate compilation and upload processes arduino-ide#1199

[codecov]

Codecov Report

Attention: Patch coverage is 32.35294% with 23 lines in your changes missing coverage. Please review.

Project coverage is 67.66%. Comparing base (ac6ec6d) to head (5bbbe80).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/mock_avrdude/main.go	0.00%	18 Missing ⚠️
commands/service_upload.go	68.75%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@ Coverage Diff @@## master #2726 +/- ## ========================================== - Coverage 67.68% 67.66% -0.03%  ========================================== Files 234 235 +1 Lines 22285 22314 +29 ========================================== + Hits 15083 15098 +15 - Misses 6017 6031 +14  Partials 1185 1185 

Flag	Coverage Δ
unit	67.66% <32.35%> (-0.03%)	⬇️

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[alessio-perugini]

Nice one! LGTM.