Remove existing ATS / "labels"-related code

[Swatinem]

A draft to remove this code from worker exists here: codecov/worker#782
This does clean up quite a bit, and in particular removes the datapoints which are saved in the report, as well as tasks related to labels.

However, in particular the label-analysis task is still being invoked from the API.

• API requests: https://codecov.sentry.io/discover/results/?id=29811&project=5215654&statsPeriod=7d
• Tasks: https://codecov.sentry.io/discover/results/?id=29810&project=4165036&statsPeriod=7d

As removing this would make report processing simpler, and the internal report format more lightweight, I would love to go ahead with this deprecation / removal.

The remaining question here, given that a low number of requests/tasks does happen, is how to go about this.

We need to figure out which customers are using this feature, and figure out if they get any value from it at all. We would then need to inform those customers that this feature is going away for good.

[Swatinem]

Here is a metabase query listing all the existing/remaining users of this feature: https://metabase.codecov.dev/question/273-labelanalysis-users