[alias-server] Support for reserved ABC aliases

Summary:
T2962

Add an array of reserved aliases that resolve to the alias registration address

Test Plan:
Review new functions and mocks. Note that abc was a previously valid registered alias but is now invalidated by the reserved alias.
npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D13232