Shrink default feature set dramatically

[alice-i-cecile]

@cart says:

In general I think we should consider moving in the direction of a smaller baseline feature set with larger "meta" features that pull in targeted collections of cargo features (ex: "3d", "2d", "dev", etc). I consider --no-default-features to be a non-viable lifestyle for people actually building apps.

From #21236 (comment)

I'm on board with this as it makes getting the right set of features a lot easier, and makes version upgrades more viable.

IMO though, this requires solving TheBevyFlock/bevy_cli#622 or rust-lang/cargo#4663 upstream, in order to reduce the level of pain involved in running our examples.

[ChristopherBiscardi]

bevy_audio is one of the most common disabled features, and likely presents a decent use case for the impact here. Here's bevy_seedling's 0.16 README instructions for how to "disable bevy_audio".

[dependencies]
bevy_seedling = "0.5"
bevy = { version = "0.16", default-features = false, features = [
  "animation",
  "bevy_asset",
  "bevy_color",
  "bevy_core_pipeline",
  "bevy_gilrs",
  "bevy_gizmos",
  "bevy_gltf",
  "bevy_mesh_picking_backend",
  "bevy_pbr",
  "bevy_picking",
  "bevy_render",
  "bevy_scene",
  "bevy_sprite",
  "bevy_sprite_picking_backend",
  "bevy_state",
  "bevy_text",
  "bevy_ui",
  "bevy_ui_picking_backend",
  "bevy_window",
  "bevy_winit",
  "custom_cursor",
  "default_font",
  "hdr",
  "multi_threaded",
  "png",
  "smaa_luts",
  "sysinfo_plugin",
  "tonemapping_luts",
  "webgl2",
  "x11",
] }

[janhohenheim]

For some other real-life examples, see headless servers, custom state impls like pyri_state, people only targeting either X11 or Wayland, and a recent interesting suggestion brought forth by IceSentry where 3D apps might skip out of all 2D things like bevy_sprite.

[atlv24]

relevant #20741