Drop support for TS < v5 -- Setup CI for type-checking all test apps

[NullVoxPopuli]

Changes

• use ember-source built in types (DT types are best effort, and not great for modern use as they are not compatible with ember-data (ember-data is compatible with the official types now))
• update the base devDep version of ember-source to support ^
• Add typescript test matrix
• Drop support for typescript < 5
  • This is because @tsconfig/ember is only compatible with TS v5, due to having verbatimModuleSyntax specified
• Test against all TS 5.x versions
  • NOTE: ember-concurrency@v2 is not compatible with the built-in ember-source types. It thinks ComputedProperty is generic (which was true from the DT types). So I've removed type-checking from the ember-concurrency test-app for now. In a future PR I think it makes sense to delete the ember-concurrency test-app entirely, because looking at the implementation of @waitFor we only happen to work with some ember-concurrency versions do to being compatible with thennables and generators -- we could probably test that stuff in isolation without ember-concurrency.
• Add overrides for certain @glimmer/* packages due to: https://github.com/glimmerjs/glimmer.js/issues/413
  • also because older versions' types are not compatible with the latest stricter tsconfig from @tsconfig/ember