[various] Add Swift Package Manager integration to example apps (#8219)
This migrates various example apps to have Swift Package Manager integration. This raises the example apps' Flutter SDK requirement to 3.24.0 or higher.
I will get a text exemption for this change.
The example apps were migrated using the following commands:
```
dart run script/tool/bin/flutter_plugin_tools.dart build-examples --ios --swift-package-manager
dart run script/tool/bin/flutter_plugin_tools.dart build-examples --macos --swift-package-manager
```
â ï¸ The following plugins' example apps are **not* included in this change as their migration included non-SPM changes that require closer review:
1. google_sign_in
1. google_sign_in_ios
1. image_picker
1. image_picker_ios
1. image_picker_macos
1. pigeon
Part of: https://github.com/flutter/flutter/issues/159173
[various] Scrub pre-iOS-13 code (#9849)
For all packages that had conditionals to support iOS <13:
- Update the min Flutter version to 3.35, which requires iOS 13
- Remove the conditional logic
- Update all the project metadata to require iOS 13+ (and macOS 10.15+ where applicable)
There is also some minor cleanup in in_app_purchase_storekit; just removing conditionals would have left cases where we were unnecessarily constructing dictionaries dynamically, so I folded them into the initial dictionary construction, and while doing that I noticed some cases where we were doing other unnecessary dynamic construction (maybe due to previous OS conditionals?) so I updated those as well. And then I noticed some inconsistency in use of WithCapacity: and updated those cases to be consistent. Lastly, I fixed a few stale comments that didn't reflect the current state of the code.
Includes autoformat changes, since updating the min Dart SDK opts into some formatter changes.
Fixes https://github.com/flutter/flutter/issues/167735
## Pre-Review Checklist
**Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the gemini-code-assist bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.
[^1]: Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling.