Add benchmarks and compile_fail tests back to workspace

[BD103]

Objective

• Our benchmarks and compile_fail tests lag behind the rest of the engine because they are not in the Cargo workspace, so not checked by CI.
• Fixes Add benchmarks and compile fail tests back to workspace #16801, please see it for further context!

Solution

• Add benchmarks and compile_fail tests to the Cargo workspace.
• Fix any leftover formatting issues and documentation.

Testing

• I think CI should catch most things!

Questions

Outdated issue I was having with function reflection being optional

The reflection_types example is failing in Rust-Analyzer for me, but not a normal check.

error[E0004]: non-exhaustive patterns: `ReflectRef::Function(_)` not covered
   --> examples/reflection/reflection_types.rs:81:11
    |
81  |     match value.reflect_ref() {
    |           ^^^^^^^^^^^^^^^^^^^ pattern `ReflectRef::Function(_)` not covered
    |
note: `ReflectRef<'_>` defined here
   --> /Users/bdeep/dev/bevy/bevy/crates/bevy_reflect/src/kind.rs:178:1
    |
178 | pub enum ReflectRef<'a> {
    | ^^^^^^^^^^^^^^^^^^^^^^^
...
188 |     Function(&'a dyn Function),
    |     -------- not covered
    = note: the matched value is of type `ReflectRef<'_>`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
126 ~         ReflectRef::Opaque(_) => {},
127 +         ReflectRef::Function(_) => todo!()
    |

I think it is because the following line is feature-gated:

bevy/examples/reflection/reflection_types.rs

Lines 117 to 122 in cc0f6a8

	// `Function` is a special trait that can be manually implemented (instead of deriving Reflect).
	// This exposes "function" operations on your type, such as calling it with arguments.
	// This trait is automatically implemented for types like DynamicFunction.
	// This variant only exists if the `reflect_functions` feature is enabled.
	#[cfg(feature = "reflect_functions")]
	ReflectRef::Function(_) => {}

My theory for why this is happening is because the benchmarks enabled bevy_reflect's function feature, which gets merged with the rest of the features when RA checks the workspace, but the #[cfg(...)] gate in the example isn't detecting it:

bevy/benches/Cargo.toml

Line 19 in cc0f6a8

bevy_reflect = { path = "../crates/bevy_reflect", features = ["functions"] }

Any thoughts on how to fix this? It's not blocking, since the example still compiles as normal, but it's just RA and the command cargo check --workspace --all-targets appears to fail.

[alice-i-cecile]

I take it the RA bug you mentioned is now fixed?

[alice-i-cecile]

Yay! And good comments too.

[BD103]

I take it the RA bug you mentioned is now fixed?

No, not yet unfortunately, and it's also surfaced in the CI failure. There are a few solutions, but I don't like any of them:

1. Conditionally-compile function reflection benchmarks, no longer enable the feature by default in benches/Cargo.toml.
2. Enable function reflection by default and assume it's available in the example.
3. Don't add benches to the Cargo workspace.
4. Change how we detect function reflection in the example. I have no idea how we'd do this, but it would be preferable.

I think this is an underlying symptom of a larger problem: feature flags are difficult to use correctly and consistently. We don't have a system for defining how and when they should be made, and it's difficult to detect when they're enabled in our examples because we tunnel features through bevy and bevy_internal.