[various] Update all packages to Pigeon 26 (#10450)
Pigeon versions <26.0.4 aren't compatible with analyzer 8.x, which is causing conflicts for flutter/flutter, so this updates the entire repo to 26.
Related: https://github.com/flutter/flutter/issues/178270
Manual fixes:
- Updates camera_android_camerax and webview_flutter_android for https://github.com/flutter/packages/pull/9515
- Adds the pigeonVar_* overrides to the url_launcher_windows tests
- Removes equality extensions to Pigeon data classes in in_app_purchase_storekit, as they are now generated by Pigeon, causing redeclaration errors.
## Pre-Review Checklist
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[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
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[^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.