Previously downloaded blobs fail to load

[mplorentz]

Sometimes blobs that we know are on disk (like the users own profile photo) fail to load. Or appear to fail to load. Maybe they are just taking so long that it seems like they failed. But loading blobs from disk does not require any interaction with the go-ssb so it shouldn't really get bottlenecked by other processes like replication.

[rabble]

Closed in PR and merged in to main