This removes all of the deprecated plugins from the tree, as well as all references to them.
They were being left in the tree only in case they needed critical fixes before the end of this year, when they will become completely unsupported and be officially discontinued on pub.dev. The end of the year is now close enough that such a release is extremely unlikely, and they are causing some maintenance burden (e.g., the tree is currently closed on an out-of-band failure in android_alarm_manager). In the event that we do have to push an emergency fix in the next several weeks, we can either temporarily restore the plugin from git history, or use a branch.
Minor related cleanup:
- Scanning the repository for remaining references turned up that `image_picker_for_web` and `video_player_for_web` had copypasta'd the package name of its example application from one of the deprecated plugins, so this fixes those names.
- Fixes `federation-safety-check` handling of top-level files in unfederated plugins that accidentally tripped federated plugin heuristics.
- Fixes `federation-safety-check` handling of deleted plugins, as it was crashing, and tests that.
- Fixes `make-deps-path-based` handling of deleted plugins, as it was crashing, and tests that.
Adds a new command that adds `dependency_overrides` to any packages in the repository that depend on a list of target packages, including an option to target packages that will publish a non-breaking change in a given diff.
Adds a new CI step that uses the above in conjunction with a new `--run-on-dirty-packages` to adjust the dependencies of anything in the repository that uses a to-be-published package and then re-run analysis on just those packages. This will allow us to catch in presubmit any changes that are not breaking from a semver standpoint, but will break us due to our strict analysis in CI.
Fixes https://github.com/flutter/flutter/issues/89862
