Final diff resolving ENG-6288, ENG-6290 and ENG-6291.
Modified Blob service multimedia upload calls to add AuthMetadata to the request.

It'd be difficult to split this into smaller parts because of required types for blob upload functions in lib.

Depends on D10912.

Extended test plan from previous diffs. Done on both web and native:

• Enabled encrypted media and blob service, sent a multimedia message
• Modified blob handlers the same way as in D10908 test plan
• Opened chat on native - the multimedia loads correctly
• (Web only) Also canceled message after the photo was preloaded - this caused "revoke holder" call on Blob service
• Made sure Blob service logs for all endpoints (get, assign_holder, upload, revoke) contain auth metadata like this:

INFO get_blob{blob_hash=xn2ILjHR45XHsbjNf_wRalWNjusWtCNntiutX1eJn0w}: blob::http::handlers::blob: Get blob request auth=UserToken(UserIdentity { user_id: "foo", access_token: "baz", device_id: "9/Dk+21eU27n7fpvFDVWqNrouje2XKGW2jtLPC7vx+A" })
`