[blob-service] Implement upload logic with new db

Summary:
Part of ENG-4269.

The code is mostly a copy-paste from http::handlers::blob::upload_blob_handler with the exception that it now accepts a stream instead of multipart form

Depends on D8454.

Test Plan: Tested later in the stack

Reviewers: michal, varun, jon, patryk

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8455