fix(AppSettings): fix group divider visuals

[rubenp02]

Description

Adds a visible divider line between settings groups. Hides dividers when there is no visible settings group on both sides to avoid duplicates.

New divider style is consistent with the existing divider between this settings page navigation list and the settings view.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)
• CI/Build changes
• Other

Testing

• Tested locally
• Added/updated unit tests
• Tested with simulator (SITL)
• Tested with hardware

Platforms Tested

• Linux
• Windows
• macOS
• Android
• iOS

Checklist

• I have read the Contribution Guidelines
• I have read the Code of Conduct
• My code follows the project's coding standards
• I have added tests that prove my fix/feature works
• New and existing unit tests pass locally

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By submitting this pull request, I confirm that my contribution is made under the terms of the project's dual license (Apache 2.0 and GPL v3).

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[rubenp02]

I'd consider the duplicate divider fix a clear bugfix that should go in the upcoming release. Let me know if the divider visuals are more of a feature and not fit for the release. But IMO, the current lack of dividers looks pretty bad. Just makes the list look like it has uneven spacing before one realizes it's because there's different sections. But that's just my opinion, of course.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 34.26%. Comparing base (f29efd3) to head (bc9e5c7).
⚠️ Report is 297 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #14896      +/-   ##
==========================================
+ Coverage   25.47%   34.26%   +8.79%     
==========================================
  Files         769      944     +175     
  Lines       65912    85200   +19288     
  Branches    30495    39315    +8820     
==========================================
+ Hits        16788    29193   +12405     
+ Misses      37285    36546     -739     
- Partials    11839    19461    +7622     

Flag	Coverage Δ
unittests	34.26% <ø> (+8.79%)	⬆️

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see 657 files with indirect coverage changes

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