edit mutation
Created by: coury-clark
Closes https://github.com/sourcegraph/sourcegraph/issues/35655
This adds support for the edit mutation for the non-global backfill. One big caveat here is that any edit will currently trigger a backfill (including superficial fields such as series label). This isn't ideal, but isn't technically blocking. I've opened https://github.com/sourcegraph/sourcegraph/issues/36499 to address this seperately.
Test plan
Created an insight, let it backfill. Then edited it and watched it generate a new backfill.