Check the folder content in new version of the agent on macos

[umbynos]

Please check if the PR fulfills these requirements

• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• Tests for the changes have been added (for bug fixes / features)

• What kind of change does this PR introduce?

bug fix

• What is the current behavior?

when uninstalling an old version of the agent (e.g. 1.2.7) a folder in ~/Applications/ArduinoCreateAgent could be left behind (empty, but existing), after uninstalling.
This will trigger this error when running a new agent:

• What is the new behavior?

The check in the new agent is performed on the existence of the ArduinoCreateAgent.app subfolder.

• Does this PR introduce a breaking change?

no

• Other information:

Partially fixes #795

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.05 ⚠️

Comparison is base (4e7b23f) 11.00% compared to head (58ee77a) 10.96%.

❗ Current head 58ee77a differs from pull request most recent head 12f5e27. Consider uploading reports for the commit 12f5e27 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #797      +/-   ##
==========================================
- Coverage   11.00%   10.96%   -0.05%     
==========================================
  Files          55       55              
  Lines        4052     4068      +16     
==========================================
  Hits          446      446              
- Misses       3551     3567      +16     
  Partials       55       55              

Flag	Coverage Δ
unit	10.96% <0.00%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
config/autostart.go	0.00% <0.00%> (ø)
main.go	2.28% <0.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[umbynos]

test release:
ArduinoCreateAgent-1.3.2-osx-amd64-installer.zip