[token-server] Fix ts lint and add to arc lint

Summary:
As I learn more about how to properly implement typescript, figuring out some initial implementations were not great. For token-server, the linter was not properly configured.

Properly configure the linter. Fix existing lint issues.

Because "properly configured" also means "works well with arclint" for ABC monorepo apps -- set that up to confirm this also works.

Test Plan: npm test, arc lint -- apps/token-server/**/*

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17174