fix: return AlreadyExists when archive exists

[dankeboy36]

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What kind of change does this PR introduce?

Bug fix

What is the current behavior?

When a client archives a sketch via gRPC and the archiveTarget already exists, the CLI correctly errors, but with the incorrect status code. The status code is 3 (illegal argument) instead of 6 (already exists).
Currently, clients must parse the error message if they want to handle the archive -> fail -> archive with override flow. This might not work reliably with translations.

What is the new behavior?

The CLI errors with the correct already exists status code when archiving a sketch, and the archive target already exists.

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

Actually, this is a breaking change, but I do not know if any client is explicitly handling status code 3. The Arduino IDE 2.x just wipes the target if it exists: https://github.com/arduino/arduino-ide/blob/4d6cfad0ff603a106efd68ffe015d6fc7449f5fc/arduino-ide-extension/src/node/sketches-service-impl.ts#L637-L639

Other information

[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.49%. Comparing base (350b0ce) to head (c0d8d27).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
commands/cmderrors/cmderrors.go	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3050      +/-   ##
==========================================
- Coverage   69.49%   69.49%   -0.01%     
==========================================
  Files         253      253              
  Lines       19166    19172       +6     
==========================================
+ Hits        13320    13324       +4     
- Misses       4615     4617       +2     
  Partials     1231     1231              

Flag	Coverage Δ
unit	69.49% <71.42%> (-0.01%)	⬇️

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