Update repo for 3.35 stable release

[stuartmorgan-g]

Does the steps listed at https://github.com/flutter/flutter/blob/master/docs/ecosystem/release/Updating-Packages-repo-for-a-stable-release.md for the 3.35 release.

This makes the minimum supported version for all packages Dart 3.7, which means it picks up the new formatter. As a result, there are massive amounts of code changes; all of it is just the result of running dart format after changing the min SDK version.

[gemini-code-assist]

Code Review

This pull request updates the minimum supported SDK version for several packages to Dart 3.7, which corresponds to Flutter 3.29. This also includes extensive formatting changes across the codebase due to the adoption of a new Dart formatter. CI configuration files and package dependencies have been updated accordingly. My review focused on the non-formatting changes, and I've noted a potential inconsistency in the changelog versioning compared to the pull request title.

[stuartmorgan-g]

I've split out #9817 for the go_router test failure.

Given the need to do that, and that there's already been a collision, I think I'll split out some sub PRs that pre-update the min SDK of some groups of packages to make this easier to land.