Enable preload on MFS commands that accept IPFS paths

[alanshaw]

Some MFS commands accept IPFS paths as input. When IPFS paths are passed, we should send a preload request so that the content can be retrieved.

Notably, the CID resolver in ipfs-http-response switched to using ipfs.files.stat instead of ipfs.object.stat (ipfs/js-ipfs-http-response#19). This means that a JS IPFS gateway currently does not send preload requests and so is useful only for fetching content the node or the preload nodes already have in their repo.

cc @lidel @achingbrain @vasco-santos

[lidel]

(late reply, just got back from vacation)

I am +1 for this: was experimenting and thinking about adding an explicit preload call for paths requested via embedded gateway in Brave, but doing it at ipfs.files.stat is even better.

Are there any cons to doing this?