Add more features to allow the removal of unused dependencies in library crates

[Green21Black]

Many bevy crates don't have features to remove unused dependencies.

Many bevy crates have features that allow using the crate without bevy, but they don't always have features for use in libraries that only need the types and not the actual functionality.

For example, bevy_transform has a bevy-support feature that can be disabled to reduce unused dependencies, but no feature that allows using Transform as a Component without also adding bevy_app as a dependency. Moreover, the bevy_app dependency is only used for the TransformPlugin, which isn't normally needed in libraries.

Solution

Add more features to bevy crates that allow more fine grained control over the dependencies used.

Additional Request

These features would also allow for something like a library feature for bevy, that can be used in libraries that don't need bevy features like Plugins or App.