[BREAKING] Remove ember-fetch

[Gaurav0]

For #442

BREAKING:

• Removes support for ember 3.28 and ember 4.4 (@ember/test-waiters 3.1.0 doesn't support)
• Removes ember-fetch as a dependency. Apps dependent on ember-fetch may have to explicitly add it to dependencies.

Uses waitForFetch from @ember/test-waiters to replace the core functionality of ember-fetch, as explained in RFC 1065

Based on #443 , please review that PR first.