Isolate testing types in Rust backend (#2810)

Testing types now live under `re_types/src/testing`, which is itself
feature gated behind the `testing` flag.

Fixes #2809 
Part of #2537 

### What

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested [demo.rerun.io](https://demo.rerun.io/pr/2810) (if
applicable)

- [PR Build Summary](https://build.rerun.io/pr/2810)
- [Docs
preview](https://rerun.io/preview/pr%3Acmc%2Frust_exclude_fuzzy/docs)
- [Examples
preview](https://rerun.io/preview/pr%3Acmc%2Frust_exclude_fuzzy/examples)

crates/re_types/Cargo.toml

@@ -14,12 +14,17 @@ version.workspace = true
 
 
 [package.metadata.docs.rs]
-all-features = true
+all-features = false
+no-default-features = true
+features = ["all"]
 
 
 [features]
 default = []
 
+## All features except `testing`.
+all = ["ecolor", "glam", "serde"]
+
 ## Enable color conversions.
 ecolor = ["dep:ecolor"]
 
@@ -29,6 +34,10 @@ glam = ["dep:glam", "dep:macaw"]
 ## Enable (de)serialization using serde.
 serde = ["dep:serde", "re_string_interner/serde"]
 
+## Include testing archetypes/components/datatypes into the crate.
+## Only useful for testing purposes.
+testing = []
+
 [dependencies]
 # Rerun
 re_error.workspace = true
@@ -74,3 +83,9 @@ re_types_builder.workspace = true
 
 # External
 rayon.workspace = true
+
+
+[[test]]
+name = "fuzzy"
+path = "tests/fuzzy.rs"
+required-features = ["testing"]

crates/re_types/src/lib.rs

@@ -471,10 +471,14 @@ impl<T> ResultExt<T> for DeserializationResult<T> {
 pub const DISPLAY_PRECISION: usize = 3;
 
 pub mod archetypes;
-mod component_name;
 pub mod components;
 pub mod datatypes;
+
+mod component_name;
 mod size_bytes;
 
 pub use component_name::ComponentName;
 pub use size_bytes::SizeBytes;
+
+#[cfg(feature = "testing")]
+pub mod testing;