[keyserver] Use blob hash to create blob URIs

Summary:
Linear task: ENG-3974.
We need to modify blob URI format to be blob-service://BLOB_HASH

This change is breaking, but I think nobody except me had any blob-service stored multimedia.

Depends on D8320

Test Plan:
With D8206 applied, and blob service messages enabled in input-state-container, I was able to upload multimedia and then view it. Used redux-devtools and console.log to ensure that messages contain the correct format in the holder/thumbnailHolder field.

Tested both web and native, both image and video

Reviewers: atul, ashoat

Reviewed By: atul

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D8321