[keyserver] Look up uploads for a message using the container column

Summary:
This is the second part of the stack to resolve ENG-1484, and is the core of it. This approach has *way* better performance.

Depends on D4673

Test Plan: I first tested this stack locally in my environment to make sure the queries worked. Then I patched it onto my production keyserver and confirmed performance was improved

Reviewers: tomek, atul

Reviewed By: tomek

Subscribers: adrian, abosh

Differential Revision: https://phab.comm.dev/D4674