[blob] Hide endpoints behind auth middleware

Summary:
Wrapped all /blob/** endpoints with auth middleware.

By the way, added /health which was missing, but it's handy for AWS ECS to do health checks (until now it treated 404 as okay)

Depends on D12414

Test Plan: Test plan for D12414 for all blob endpoints. /health works without auth

Reviewers: varun, will, kamil

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12415