[Cashtab] Remove legacy aliases implementation

Summary:
chronik and Cashtab dev have progressed beyond this implementation approach. When aliases go into prod, they will not be implemented in this way -- instead we will use a chronik plugin.

Remove legacy alias implementation code from Cashtab. Keeping this code up to date with other Cashtab improvements is not worth the effort.

Test Plan: npm test

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D17399