Update the autostart file when it's required

[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?

fix corner case introduced in #781

• What is the current behavior?

Fix #788, the agent is now able to detect if the autostart file needs to be overwritten or not

• What is the new behavior?

The agent is now able to update the autostart file when it's required.

• Does this PR introduce a breaking change?

no

• Other information:

[codecov-commenter]

Codecov Report

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

Comparison is base (4e7b23f) 11.00% compared to head (038acf6) 10.96%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #791      +/-   ##
==========================================
- Coverage   11.00%   10.96%   -0.05%     
==========================================
  Files          55       55              
  Lines        4052     4069      +17     
==========================================
  Hits          446      446              
- Misses       3551     3568      +17     
  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)

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[umbynos]

Testable artifact here https://github.com/arduino/arduino-create-agent/releases/tag/1.2.8-rc12