refactor requests to use a modern node requests library instead of `node-fetch`

[rafaelcr]

There are newer request libraries such as undici that are much more easy to work with when it comes to JSON parsing, request/response schema validation, status code and headers handling, etc.

The registrar should be updated to use one of these librares so it can abstract away this logic when calling the Stacks API. Another option is to use the Stacks Blockchain API client to issue these calls.