Fix integration of AppCenter

[fortmarek]

Resolves #4024

Short description 📝

I added the umbrella header as the public header in Xcode, but we should rely on header search paths only. With the umbrella header set as public, the PLCrashReporter dependency does not build because the imports in the internal header files that try to use the module import instead of the filename import:

#if __has_include(<CrashReporter/CrashReporter.h>) // this should be false when compiling the `PLCrashReporter` module
#import <CrashReporter/CrashReporter.h>
#import <CrashReporter/PLCrashReporter.h>
#else // These are the imports that we want to use
#import "CrashReporter.h"
#import "PLCrashReporter.h"
#endif

How to test the changes locally 🧐

You should be able to run and build the app_with_spm_dependencies fixture

Contributor checklist ✅

• The code has been linted using run mise run lint:fix
• The change is tested via unit testing or acceptance testing, or both
• The title of the PR is formulated in a way that is usable as a changelog entry
• In case the PR introduces changes that affect users, the documentation has been updated

Reviewer checklist ✅

• The code architecture and patterns are consistent with the rest of the codebase
• Reviewer has checked that, if needed, the PR includes the label changelog:added, changelog:fixed, or changelog:changed, and the title is usable as a changelog entry

[mikeger]

Thanks for fixing AppCenter integration 👍