refactor(loader): move component definition code to the `$compileProvider`

The `Module.component()` helper now delegates to `$compileProvider.component()`.

This has the following benefits:

- when using only the loader, we are not accessing out of scope variables / functions
- components can be registered via $compileProvider
- docs are a bit easier to find
- it is easier to keep the Batarang version of the loader up to date if there is minimal
  code in that file.

Closes #13692