Assets as Entities

## Goal Description

`bevy_asset` implements a bespoke storage system for assets. This is both redundant, less powerful, and less flexible than Bevy's ECS. Assets-as-entities aims to represent assets as entities! This allows us to:

1) Remove our bespoke storage system.
2) Take advantage of ECS optimizations that are implemented.
3) Provide a more ergonomic interface for assets for users.
4) Allow users to extend asset data with their own components.

## Goal Status

This is a potential [Bevy Project Goal](https://bevy.org/learn/contribute/project-information/project-goals/). Its state on the [Project Goals Board](https://github.com/orgs/bevyengine/projects/23/views/1) determines if it is Proposed, Postponed, Blocked (Approved), Inactive (Approved), Active (Approved), Completed, or Declined.

- **Staffing SMEs**: @andriyDev, @cart
- **Working Group Link**: [Link](https://discord.com/channels/691052431525675048/1476701089746255912)
- **Design Documents**: Design documents not yet written