Upgrade Spezi to 0.8.0 and move to Observable

[Supereg]

Upgrade Spezi to 0.8.0 and move to Observable

♻️ Current situation & Problem

This PR upgrades Spezi to the latest 0.8.0 release. Further, we migrate our codebase to use the new observation framework.

⚙️ Release Notes

• Migrate to Observation
• Updated Spezi to 0.8.0

📚 Documentation

Minor fixes in the documentation.

✅ Testing

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📝 Code of Conduct & Contributing Guidelines

By submitting creating this pull request, you agree to follow our Code of Conduct and Contributing Guidelines:

• I agree to follow the Code of Conduct and Contributing Guidelines.

[codecov]

Codecov Report

Merging #13 (7d5ef67) into main (f8f6645) will increase coverage by 0.20%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
+ Coverage   71.79%   71.99%   +0.20%     
==========================================
  Files          11       11              
  Lines         436      439       +3     
==========================================
+ Hits          313      316       +3     
  Misses        123      123              

Files	Coverage Δ
...s/SpeziHealthKit/CollectSample/CollectSample.swift	100.00% <ø> (ø)
.../SpeziHealthKit/CollectSample/CollectSamples.swift	100.00% <ø> (ø)
...hKit/CollectSample/HealthKitSampleDataSource.swift	96.33% <100.00%> (ø)
...Extensions/HKHealthStore+AnchoredObjectQuery.swift	85.19% <100.00%> (ø)
Sources/SpeziHealthKit/HealthKit.swift	88.89% <100.00%> (+0.49%)	⬆️
...hKitDeliverySetting/HealthKitDeliverySetting.swift	100.00% <ø> (ø)

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[PSchmiedmayer]

Thank you @Supereg!