Merge HasBufFS into HasFS

[jorisdral]

No description provided.

[jorisdral]

My thinking here is that we can safely remove this module and refrain from exposing System.FS.Sim.Prim because these modules are not currently used by ouroboros-consensus or lsm-tree. It's more useful for those packages to use simHasFS or simErrorHasFS instead. However, if in the future there would be a request to expose parts of the System.FS.Sim.Prim module, we can do that then. For now, I'm in favour of applying the YAGNI principle

[jasagredo]

Perhaps it already exists and I didn't notice, but I think it would be useful to have a list somewhere with the 3-4 types of FSs this library exposes and when to use one or the other.

[jorisdral]

Perhaps it already exists and I didn't notice, but I think it would be useful to have a list somewhere with the 3-4 types of FSs this library exposes and when to use one or the other.

The fs-api README and fs-sim README mention the available ones. That also reminds me that I should update those to account for the now removed pureHasFS!

[jasagredo]

Thanks!