V2 addon

[BobrImperator]

• Migrates ESA to v2 addon
• introduces 'test-esa' package which is the extracted tests from ember-simple-auth implementation.
• fixes mock server
• Removes import fetch from 'fetch' from ESA, we're using native fetch now.
• Wraps async functions with @ember/test-waiters
• Copies README and LICENSE to the project during deploy
• Sets pnpm resolution-mode to highest
  https://pnpm.io/npmrc#resolution-mode
• Removes usage of Ember.testing and uses isTesting macro instead
• Removes ember-get-config seems to not be working in v2 addons
• Removes remaining global Ember references

[BobrImperator]

Thanks @mansona @lolmaus @NullVoxPopuli for the help!