Using reverted changesets for model training

Nobody has claimed this yet.

Per text with @batpad,

## Changeset comment has `revert`

There are a total of `13,125` changesets on osmcha with **`revert`** in the changeset comment. Interestingly, `2,505` (20%) changesets are one feature modification changesets which is what we use in the latest version of Gabbar.

- [One feature changesets with `revert` in changeset comment](https://osmcha.mapbox.com/?create__gte=0&create__lte=0&modify__gte=1&modify__lte=1&delete__gte=0&delete__lte=0&comment__icontains=revert&is_suspect=False&is_whitelisted=All&checked=All&all_reason=True)

Assuming, mappers revert a problematic or wrong feature in these one feature modification changesets, this could be an additional dataset we could make use of for the current iteration of the feature level classifier of Gabbar. I manually :eyes: a couple of these changesets and they are definitely want we want to catch with Gabbar.

- https://osmcha.mapbox.com/49465923

- https://osmcha.mapbox.com/49442894

## Changesets from revert user accounts

Mappers and DWG sometimes maintain a separate account for reverts. Changesets from these accounts will be interesting to look at as well. Ex:

- https://www.openstreetmap.org/user/SomeoneElse_Revert/history

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cc: @anandthakker @geohacker

The issue does not name files or tests. Start by reviewing Gabbar's current feature-level classifier training workflow, then inspect the linked OSMCha changesets and revert-user examples. Done means defining whether and how reverted changesets should become training data, with an agreed scope for both comment-based and account-based sources.

Written by the indexing model from the issue text.