fix: SentrySwiftUI Carthage build import

[nekrich]

📜 Description

tl;dr; Fixed SentrySwiftUI Carthage build import.

Since there is no modulemap for the SentrySwiftUI declaring exported submodules:

1. For Carthage build make @_implementationOnly import SentryInternal.
2. Import SentrySwiftUI xcframework Samples/Carthage-Validation/XCFramework project to check imports.

💡 Motivation and Context

Can't import prebuild SentrySwiftUI.xcframework. Got a No such module 'SentryInternal' error.

🖼️ Screenshot

At first I thought it's library evolution again, but it was broken imports inside a private swift interface file.

💚 How did you test it?

1. Run make build-xcframework to create xcframework.
2. Import SentrySwiftUI.xcframework into a Samples/Carthage-Validation/XCFramework project.
3. Build Samples/Carthage-Validation/XCFramework project.

📝 Checklist

You have to check all boxes before merging:

• I reviewed the submitted code.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.881%. Comparing base (1ee3d54) to head (39d4610).

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3817       +/-   ##
=============================================
+ Coverage   90.877%   90.881%   +0.004%     
=============================================
  Files          559       559               
  Lines        44054     44054               
  Branches     15701     15692        -9     
=============================================
+ Hits         40035     40037        +2     
+ Misses        3949      3838      -111     
- Partials        70       179      +109     

see 29 files with indirect coverage changes

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[brustolin]

Hello @nekrich, thanks for the help with this PR!!