[util-macros] Add tests for serde and TagAwareDeserialize behavior

Summary:
Added tests to demonstrate both serde issue described in ENG-8901 and the macro introduced in D12901

Depends on D12901

Test Plan: cargo test

Reviewers: varun, will, kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12902