move scene.json data inside Project type

### Problem:
We are currently spreading props from `scene.json` into the `Project` type to provide info about the project + scene. The problem with this approach is that whenever the `scene.json` get's updated, we need to map those updates to the Project type.
Example:

This is a bug prone approach since forgetting to map a prop will leave the in-memory Project outdated.

### Solution:
Change `Project` type to include the whole `Scene` type as `{ ...project, scene: Scene }`, and replace all the current scene.json-based props from `Project` type with getter functions so we avoid duplicating data as we do now.
By replacing current scene.json-based props I mean props like `title`, which is an alias for `scene.display?.title`, etc. Those props can instead be a `getTitle` function that returns `project.scene.display?.title || 'Some default'`.

So if an update happens to the `scene.json` file, then for updating the in-memory project and have everything in-sync this will be enough: