Gitaly's [`SetFullPath`](https://gitlab.com/gitlab-org/gitaly/-/blob/a3a94460be05799fdb5f9b4d1dab7832fe556bcd/internal/gitaly/service/repository/fullpath.go#L17) is used by Rails to store the repository's project path inside the repository's git config. This is mainly done to have some human readable identifier in the repository should the database mappings from the hashed path to project path be lost. In https://gitlab.com/groups/gitlab-org/-/epics/8903, we'd have to replicate this config value across the replicas, which involves quite a bit of logic to properly support everywhere with regards to write-ahead logging, MVCC and checksumming. We'd also like to keep the git config local to a replica, so we'd want to store this value somewhere else. Through the conversation in https://gitlab.com/gitlab-org/gitaly/-/issues/4521, we've come to a conclusion that we don't want to keep supporting this feature: 1. It's better to push users to maintain proper backups. With proper backups, one would always have the project path backed up along with the rest of the database. 2. The full path in the repository can be stale and out of sync with the project path in Rails DB. It shouldn't be relied on. This epic tracks the work to remove `gitlab.full_path` from the repository's git config, removing its usage and removing the associated `SetFullPath` and `FullPath` RPCs.