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During peer recoveries, we need to copy over lucene files and replay the operations they miss from the source translog. Guaranteeing that translog files are not cleaned up has seen many iterations overtime. Back in the old 1.0 days, recoveries went through the Engine and actively prevented both translog cleaning and lucene commits. We then moved to a notion called Translog Views, which allowed the recovery code to "acquire" a view into the translog which is then guaranteed to be kept around until the view is closed. The Engine code was free to commit lucene and do what it ever it wanted without coordinating with recoveries. Translog file deletion logic was based on reference counting on the file level. Those counters were incremented when a view was acquired but also when the view was used to create a `Snapshot` that allowed you to read operations from the files. At some point we removed the file based counting complexity in favor of constructs on the Translog level that just keep track of "open" views and the minimum translog generation they refer to. To do so, Views had to be kept around until the last snapshot that was made from them was consumed. This was fine in recovery code but lead to [a subtle bug](https://github.com/elastic/elasticsearch/pull/25862) in the [Primary Replica Resyncer](https://github.com/elastic/elasticsearch/pull/25862). Concurrently, we have developed the notion of a `TranslogDeletionPolicy` which is responsible for the liveness aspect of translog files. This class makes it very simple to take translog Snapshot into account for keep translog files around, allowing people that just need a snapshot to just take a snapshot and not worry about views and such. Recovery code which actually does need a view can now prevent trimming by acquiring a simple retention lock (a `Closable`). This removes the need for the notion of a View.