Performance: use content streaming when loading files from storage

[gdorsi]

When loading big files from storage we can observe two issues.

First, the content is processed all at once, blocking the main thread:

Second, if the content isn't fully uploaded on the first session, on reload it will be sent as a single content message making the upload very likely to fail.

We should change the collectCoValueData function on cojson-storage to make use of the signature streaming to split the coValue content in chunks.

This way the processing would be done per-chunk not blocking the main thread and so the content upload.