Remove extraneous mod statements from tests (#975)

Integration tests are compiled into their own binaries, which are then
executed. As such, there's no need to wrap integration tests in modules:

```rust
// in `tests/some_test.rs`
use some::dependency;

#[cfg(test)]
mod some_integration_test {
  use super::*;

  // Some tests go here.
}
```

This is common practice in unit tests, which if not gated behind a
`cfg` flag are included in the final release binary. We were mistakenly
doing the same thing in integration tests, where it was unnecessary.

nativelink-config/BUILD.bazel

@@ -35,6 +35,7 @@ rust_test_suite(
         "//nativelink-error",
         "@crates//:byte-unit",
         "@crates//:humantime",
+        "@crates//:pretty_assertions",
         "@crates//:serde",
         "@crates//:serde_json5",
     ],

nativelink-config/Cargo.toml

@@ -9,3 +9,6 @@ humantime = "2.1.0"
 serde = { version = "1.0.198", features = ["derive"] }
 serde_json5 = "0.1.0"
 shellexpand = "3.1.0"
+
+[dev-dependencies]
+pretty_assertions = "1.4.0"

nativelink-config/tests/deserialization_test.rs

@@ -15,6 +15,7 @@
 use nativelink_config::serde_utils::{
     convert_data_size_with_shellexpand, convert_duration_with_shellexpand,
 };
+use pretty_assertions::assert_eq;
 use serde::Deserialize;
 
 #[derive(Deserialize)]
@@ -29,43 +30,38 @@ struct DataSizeEntity {
     data_size: usize,
 }
 
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_duration_human_readable_deserialize() {
-        let example = r#"
+#[test]
+fn test_duration_human_readable_deserialize() {
+    let example = r#"
             {"duration": "1m 10s"}
         "#;
-        let deserialized: DurationEntity = serde_json5::from_str(example).unwrap();
-        assert_eq!(deserialized.duration, 70);
-    }
+    let deserialized: DurationEntity = serde_json5::from_str(example).unwrap();
+    assert_eq!(deserialized.duration, 70);
+}
 
-    #[test]
-    fn test_duration_usize_deserialize() {
-        let example = r#"
+#[test]
+fn test_duration_usize_deserialize() {
+    let example = r#"
             {"duration": 10}
         "#;
-        let deserialized: DurationEntity = serde_json5::from_str(example).unwrap();
-        assert_eq!(deserialized.duration, 10);
-    }
+    let deserialized: DurationEntity = serde_json5::from_str(example).unwrap();
+    assert_eq!(deserialized.duration, 10);
+}
 
-    #[test]
-    fn test_data_size_unit_deserialize() {
-        let example = r#"
+#[test]
+fn test_data_size_unit_deserialize() {
+    let example = r#"
             {"data_size": "1KiB"}
         "#;
-        let deserialized: DataSizeEntity = serde_json5::from_str(example).unwrap();
-        assert_eq!(deserialized.data_size, 1024);
-    }
+    let deserialized: DataSizeEntity = serde_json5::from_str(example).unwrap();
+    assert_eq!(deserialized.data_size, 1024);
+}
 
-    #[test]
-    fn test_data_size_usize_deserialize() {
-        let example = r#"
+#[test]
+fn test_data_size_usize_deserialize() {
+    let example = r#"
             {"data_size": 10}
         "#;
-        let deserialized: DataSizeEntity = serde_json5::from_str(example).unwrap();
-        assert_eq!(deserialized.data_size, 10);
-    }
+    let deserialized: DataSizeEntity = serde_json5::from_str(example).unwrap();
+    assert_eq!(deserialized.data_size, 10);
 }