Regenerate protobuf as part of default task

[nex3]

No description provided.

[ntkme]

I'm afraid that this will break linux/android release pipelines. For example, for android it builds protobuf on dart:latest container and then build the binary on ghcr.io/dart-android/dart:latest container. The reason is that there is simply no prebuilt binary of buf for android (bionic libc).

[nex3]

I don't think those tasks use the default pub run grinder task, I think they explicitly call out to the tasks they need. The default task is really meant for human convenience.