Fix bevy_remote not compiling on wasm (#23367)

# Objective

- Make it possible to enable `bevy_remote` feature on wasm target
without the `bevy_remote/http` feature (which doesn't compile on wasm),
thus allowing to use the transport-agnostic `RemotePlugin`.
- Retain behavior of `bevy_remote` having the `bevy_remote/http` feature
by default on non-wasm targets, so no breaking changes for users.

## Solution

- Disable default features (so no `http`) in
`bevy_internal/bevy_remote`.
- Enable default features (including `http`) on non-wasm builds in
`bevy_internal/bevy_remote`.
- Fix `bevy_remote` having some dependencies only used by the HTTP
transport (and not wasm-compatible) not under the `http` feature flag.

## Testing

Tested locally with a temporary example not included in this PR that
enabled `bevy_remote`, added `RemotePlugin` but not `RemoteHttpPlugin`,
and verified that it compiled for both native and wasm targets, as well
as building the other bevy_remote examples on native.

---

Try yourself by creating a new crate with the following dependencies on
`Cargo.toml`:

```toml
[dependencies]
bevy = { git = "https://github.com/splo/bevy.git", branch = "fix-bevy_remote-wasm", features = [
    "bevy_remote",
] }
```

Add the following to `main.rs`:

```rust
use bevy::{prelude::*, remote::RemotePlugin};

fn main() {
    App::new().add_plugins(DefaultPlugins).add_plugins(RemotePlugin::default()).run();
}
```

And build both for native and wasm targets to verify it compiles
successfully.

```shell
cargo build --target wasm32-unknown-unknown # Fails on main branch.
cargo build
```

Author: splo

crates/bevy_internal/Cargo.toml

@@ -532,7 +532,10 @@ bevy_input_focus = { path = "../bevy_input_focus", optional = true, version = "0
 bevy_pbr = { path = "../bevy_pbr", optional = true, version = "0.19.0-dev" }
 bevy_picking = { path = "../bevy_picking", optional = true, version = "0.19.0-dev" }
 bevy_settings = { path = "../bevy_settings", optional = true, version = "0.19.0-dev" }
-bevy_remote = { path = "../bevy_remote", optional = true, version = "0.19.0-dev" }
+bevy_remote = { path = "../bevy_remote", optional = true, version = "0.19.0-dev", default-features = false, features = [
+  "bevy_asset",
+  "bevy_render",
+] }
 bevy_render = { path = "../bevy_render", optional = true, version = "0.19.0-dev" }
 bevy_world_serialization = { path = "../bevy_world_serialization", optional = true, version = "0.19.0-dev" }
 bevy_scene2 = { path = "../bevy_scene2", optional = true, version = "0.19.0-dev" }
@@ -554,6 +557,10 @@ bevy_winit = { path = "../bevy_winit", optional = true, version = "0.19.0-dev",
 [target.'cfg(target_os = "android")'.dependencies]
 bevy_android = { path = "../bevy_android", version = "0.19.0-dev", default-features = false }
 
+# Only enable bevy_remote/http (default features) on non-WASM targets.
+[target.'cfg(not(target_family = "wasm"))'.dependencies]
+bevy_remote = { path = "../bevy_remote", version = "0.19.0-dev", default-features = true, optional = true }
+
 [lints]
 workspace = true
 

crates/bevy_remote/Cargo.toml

@@ -10,7 +10,13 @@ keywords = ["bevy"]
 
 [features]
 default = ["http", "bevy_asset", "bevy_render"]
-http = ["dep:async-io", "dep:smol-hyper", "bevy_tasks/async-io"]
+http = [
+  "dep:async-io",
+  "dep:hyper",
+  "dep:smol-hyper",
+  "dep:http-body-util",
+  "bevy_tasks/async-io",
+]
 bevy_asset = ["dep:bevy_asset"]
 bevy_render = ["dep:bevy_render"]
 
@@ -37,16 +43,16 @@ bevy_log = { path = "../bevy_log", version = "0.19.0-dev" }
 
 # other
 anyhow = "1"
-hyper = { version = "1", features = ["server", "http1"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1.0.140"
-http-body-util = "0.1"
 async-channel = "2"
 
 # dependencies that will not compile on wasm
 [target.'cfg(not(target_family = "wasm"))'.dependencies]
 async-io = { version = "2", optional = true }
+hyper = { version = "1", optional = true, features = ["server", "http1"] }
 smol-hyper = { version = "0.1", optional = true }
+http-body-util = { version = "0.1", optional = true }
 
 [lints]
 workspace = true