[keyserver] Test impact of introduction of isAdminRole on Ashoat's ThreadStore

Summary:
This diff stack introduces a script that tests various different approaches to reducing the size of the ThreadStore. We may or may not land it... the goal is just to get some numbers.

Depends on D9337

Test Plan:
Run the script:

after introducing isAdminRole, Ashoat's ThreadStore is 14839491 bytes large

Corresponds to 14.15 MiB, which is a reduction of 79.50%.

Reviewers: atul, tomek

Reviewed By: atul

Differential Revision: https://phab.comm.dev/D9338