Handle GET range-requests in the file system layer

[ishank011]

Range-based downloads should be handled by the file systems. Instead of transporting large files to the ocdav layers for small ranges, these should be truncated earlier as per the functionalities provided by the fs.

[butonic]

um did I miss anything in #1388?

[butonic]

Ah, you are talking about the storage interface.

[ishank011]

@butonic yep, currently we read the complete file from the file system and truncate it later. We were discussing the possibility of having this functionality in EOS so as to avoid streaming the whole file. So different file systems would handle it differently (they already do so for range-based uploads via tus), so it makes sense to move this implementation detail there.