Switch precache to better locality check

[lidel]

Right now we list all local CIDs via ipfs refs local and its not efficient to do on a big repo:

https://github.com/ipfs-shipyard/ipfs-companion/blob/793bd6cdbe804f611ed42f7dd32c6fb8d9d224b8/add-on/src/lib/precache.js#L36-L40

Idea A

As noted here we could improve inRepo check and run regular ipfs refs -r --offline if there was no error that means the entire DAG is present in local repo.

Caveat: --offline works only in go-ipfs CLI, missing from JS API does not https://github.com/ipfs/js-ipfs/blob/master/docs/core-api/REFS.md#ipfsrefslocaloptions

Idea B

below works in go-ipfs, showing % of local vs remote ipfs files stat --with-local --size /ipfs/bafybeigkbbjnltbd4ewfj7elajsbnjwinyk6tiilczkqsibf3o7dcr6nn4

Idea C

ipfs block stat --offline <cid> will return error if CID is not already present in the datastore

TODO: check if implemented in js-ipfs and updated this forum thread for visibility.