Make osu!framework use the ECS Paradigm

[sr229]

As it stands right now there's some things fundamentally broken which is a major roadblock on Vignette. We're going to fix one of them, and one of those is the draw hierarchy, because right now the inheritance in the hierarchy doesn't make sense.

[sr229]

TODO

• Implement Component and Composite<T>
• Implement osu.Framework.Primitives.
• Port everything that belongs as a Primitive on said namespace

More guidance at ppy/osu-framework#4281

[sr229]

Assigned to Encore 1

[LeNitrous]

Changed the title as it affects more than the draw hierarchy at this point, after a discussion with @sr229 here's the proposed structure:

[sr229]

We have committed on Encore to use a different approach. Closing as wontfix.