Replace term whitelist with allowlist

[kiwiupover]

I followed the RFC from awhile back that has since been merged, so hopefully this can be changed here in ember-cli-fastboot as well.

This PR pushes @mcfiredrill work over the line https://github.com/ember-fastboot/ember-cli-fastboot/pull/806

Closes #806

[mcfiredrill]

Thank you so much! Sorry I must have missed your previous comment. https://github.com/ember-fastboot/ember-cli-fastboot/pull/806#issuecomment-769917539

Let me know if I can help with anything and feel free to close the previous PR #806

[bertdeblock]

Is this in response to the Replace terms blacklist & whitelist in Ember CLI RFC? If so, I thought the settled upon terms were include and exclude? If not, please ignore me 😄.

[xg-wang]

fastboot has already released v3, as a minor bump we can have an alias for the old name (with deprecation would be even better); for ember-cli-fastboot it seems fine to include a breaking change, as the public interface in config is straight forward, i.e., test-packages/basic-app/config/environment.js Do we want to include the change in https://github.com/ember-fastboot/ember-cli-fastboot/milestone/2?

[mansona]

@xg-wang I would feel quite strongly against releasing a breaking change for this in a major version that has never been deprecated once since that's not how we usually do things in Ember. I think it's totally fine for the alias and the deprecation to live for the entirety of the 3.x series 👍 especially since it won't be a massive code-path that needs to still hang around, as we can use the new name internally and just make sure that we are reading from the old name as a fallback

[kiwiupover]

@mansona I have fixed the requested changes for this PR. Can you please review again.