Add support for range requests to Fetch

[james-pre]

This is a PR to track the progression of #53.

The implementation in 50e600d involves some changes to transactions that are not backwards type compatible and not runtime forward compatible. Due to the significance of these changes, I've labeled the PR as breaking.

Tests have not been changed at all and are passing, so that is good at least.

[james-pre]

One issue that will likely need to be fixed is making sure the cache can keep track of which ranges have been fetched. At the moment, the un-fetched ranges would be zeroed out, and the current behavior would result in a read of the zeroed data without fetching it first.

@zardoy, this will likely tie into streaming zip files, or at least fetching them in parts. @coder0107git mentioned this in zen-fs/archives#3. Do either of you have any feedback?

@mcandeia, I know you aren't using Fetch directly, but this PR also impacts the underlying transaction structure and behavior. Are you depending on this in any way? If so, would you be willing to upgrade even with breaking changes to the internal API? It would mean you can do partial reads and writes and the transaction level. Please let me know your thoughts.

[zardoy]

this will likely tie into streaming zip files, or at least fetching them in parts. @coder0107git mentioned this in zen-fs/archives#3. Do either of you have any feedback?

I just want zip data so badly. Yes making fetch automatically work with this would be beneficial

[james-pre]

I think a nice solution to the caching problem I mentioned earlier is adding the offset/end to fetchFile, which can be used by ZipFS. Then fetchFile can handle the reads, writes, and storage.

[james-pre]

The actual support for range requests has been implemented over on Utilium (james-pre/utilium@4c82012) so it can be used in other projects (not just ZenFS).

[zardoy]

I just want zip data so badly.

Sorry I meant zip data streaming (zen-fs/archives#3)