This hopefully clears up, at least for the use of the FileSinkWriteExt
trait the relationship between `auto_commit` and `roll_time`. There is
no default implementaion for this option, as all options have
implications that should be considered.

The PR that updated FileSink to use the Ext trait had an incorrect
understanding of the relationship between `roll_time` and `auto_commit`.

That understanding has since been corrected and codified in the
`FileSinkCommitStrategy` enum.

For this commit, https://github.com/helium/oracles/pull/849/files was
combed through to get all correct settings for FileSinks before they
were transitioned to use FileSinkWriteExt::file_sink().

* Change so auto_commit and roll_time are separated

* Create FileSinkRollTime enum