[native] Add function to upload media to blob service

Summary:
This diff adds a function that calls all necessary endpoints to upload a media file to Blob service. It has 3 stages:

1. Create a holder and assign it to a blob (identified by blob hash)
2. If the blob content doesn't exist yet, upload it
3. When the above succeeds, upload blob metadata to keyserver

Depends on D7620, D7648

Test Plan: This function is called and tested in the next diff.

Reviewers: atul, marcin

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D7649