Make sure generated code is up to date in PRs

[heaths]

Like in other languages, we need a way to make sure that generated code is up to date with the configured emitter version in the repo. This should fail the build and ask people to regenerate. We should constrain it to just the crates they touched. Plenty of precedent to draw upon from other languages.

Possibly related to #1972.

[RickWinter]

@heaths Can you provide more context on what type of problems we want to prevent. In Go we don't do anything to enforce the generated code is up to date with latest emitters.

[heaths]

To my knowledge, every other language does. It's to make sure that people don't update the tsp-location.yml and forget to regenerate or, more importantly, if we make an emitter change and then someone submits a new PR, they should regenerate on that particular change. It's to make sure we ship what is intended, and is part of the release pipelines for that very reason for other languages.

[heaths]

We discussed this in a meeting today and arrived at the conclusion this is actually a good thing, Like most other languages, we'll run the emitter against the tsp-locations.yml and then run git diff -- sdk/{service directory}. If there are any differences, fail the build. Practically, this will only affect PRs where the files within a pipeline/service directory are changing so only those get checked. This way, we make sure that the service partners have rerun the generator and picked up the latest version configured in eng/emitter-package.json and have all the latest, greatest, most-secure features before they possibly ship.