[QUEST] v7 Release

[bertdeblock]

When fixing CI over in #775, I noticed this project has a few fallbacks in place for older versions of various packages (ember-cli, ember-source, ember-cli-babel, ember-cli-htmlbars-inline-precompile, ...).
Maybe it's a good idea to clean those up, to make maintenance a bit easier?

Suggestion checklist:

• Remove support for Node v12 and v14:
  Drop support for Node v12 and v14, add support for Node v16, v18 and v20 #777
• Add support for Node v16, v18 and v20:
  Drop support for Node v12 and v14, add support for Node v16, v18 and v20 #777
• Remove globalThis check (always available since Node v12):
  Drop support for Node v12 and v14, add support for Node v16, v18 and v20 #777
• Remove support for ember-cli versions below v3.13
• Remove support for ember-source versions below v3.28
• Remove support for ember-cli-babel versions below v7.11
• Remove fallback for ember-cli-htmlbars-inline-precompile and/or error when present?