[lib][keyserver] Move output validators tests to lib

Summary:
issue: ENG-8060
in stack ending with D11945 I moved all output validators to lib. We can also move their tests now

Test Plan: Run yarn jest in keyserver/ and lib/

Reviewers: tomek, kamil, bartek

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11958