[nextest-runner] use an IndexMap for JUnit aggregation

Test suites that run first are now stored first in the JUnit output. Previously
this was effectively in completely random order, which doesn't seem right.

nextest-runner/src/reporter/aggregator/junit.rs

@@ -14,11 +14,12 @@ use crate::{
     test_output::{ChildExecutionOutput, ChildOutput},
 };
 use debug_ignore::DebugIgnore;
+use indexmap::IndexMap;
 use nextest_metadata::RustBinaryId;
 use quick_junit::{
     NonSuccessKind, Report, TestCase, TestCaseStatus, TestRerun, TestSuite, XmlString,
 };
-use std::{collections::HashMap, fmt, fs::File};
+use std::{fmt, fs::File};
 
 static STDOUT_STDERR_COMBINED: &str = "(stdout and stderr are combined)";
 static STDOUT_NOT_CAPTURED: &str = "(stdout not captured)";
@@ -28,14 +29,14 @@ static PROCESS_FAILED_TO_START: &str = "(process failed to start)";
 #[derive(Clone, Debug)]
 pub(super) struct MetadataJunit<'cfg> {
     config: JunitConfig<'cfg>,
-    test_suites: DebugIgnore<HashMap<SuiteKey<'cfg>, TestSuite>>,
+    test_suites: DebugIgnore<IndexMap<SuiteKey<'cfg>, TestSuite>>,
 }
 
 impl<'cfg> MetadataJunit<'cfg> {
     pub(super) fn new(config: JunitConfig<'cfg>) -> Self {
         Self {
             config,
-            test_suites: DebugIgnore(HashMap::new()),
+            test_suites: DebugIgnore(IndexMap::new()),
         }
     }
 
@@ -203,7 +204,7 @@ impl<'cfg> MetadataJunit<'cfg> {
                     .set_report_uuid(run_id)
                     .set_timestamp(start_time)
                     .set_time(elapsed)
-                    .add_test_suites(self.test_suites.drain().map(|(_, testsuite)| testsuite));
+                    .add_test_suites(self.test_suites.drain(..).map(|(_, testsuite)| testsuite));
 
                 let junit_path = self.config.path();
                 let junit_dir = junit_path.parent().expect("junit path must have a parent");