[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.
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[various] Update min iOS/macOS versions (#10231)
For all packages that have not already done so:
- Ensure that the minimum iOS version is 13.
- Ensure that the minimum macOS version is 10.15.
- Ensure that the minimum Flutter SDK version in 3.35 for anything with changes from the above.
In https://github.com/flutter/packages/pull/9849 I did the iOS plugins that had conditional logic for iOS <13, but I forgot to follow up with updating the minimum for the plugins that didn't have conditional logic.
Because this changes min Dart SDKs, it causes autoformat changes. There are no actual code changes in this PR; all Dart file changes are purely the result of re-running dart format.
This does bump the versions, even though repo policy would allow skipping version bumps for only changing min requirements, just to avoid conflating all the changes here with future releases.
Part of https://github.com/flutter/flutter/issues/167735
Part of https://github.com/flutter/flutter/issues/167745
## Pre-Review Checklist
[^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.