Update crate references in codegen tests

Update imports to use `roto_tonic` instead of `crate` for BufferPool
and StatusBody. Remove the broad replacement of `crate` with `roto`
and add error output to `test_map_build.rs`.

codegen/tests/test_helloworld_build.rs

@@ -55,12 +55,12 @@ fn test_helloworld_generated_code_builds() {
     // 4. Write the generated code to src/lib.rs
     let mut all_code = String::new();
     for (_, content) in generated_files {
-        all_code.push_str(&content);
+        let replaced = content.replace("use crate::{BufferPool, StatusBody};", "use roto_tonic::{BufferPool, StatusBody};");
+        all_code.push_str(&replaced);
         all_code.push_str("\n");
     }
-    let final_code = all_code.replace("use crate::", "use roto::");
     let lib_path = temp_project_dir.join("src/lib.rs");
-    fs::write(lib_path, final_code).expect("Failed to write generated code to src/lib.rs");
+    fs::write(lib_path, all_code).expect("Failed to write generated code to src/lib.rs");
 
     // 5. Attempt to build the project
     let build_status = Command::new("cargo")