[ddc] Update hot reload test names in results

Makes the test results more predictable and easier to search for
by matching the pattern of other test suites.

Examples:
`tests/reload//b/s/w/ir/cache/builder/sdk/tests/hot_reload/const_to_non_const_class/main.1.dart-diff`
  becomes `hot_reload/const_to_non_const_class/main.1.dart-diff`

`tests/reload/const_to_non_const_class` becomes
  `hot_reload/const_to_non_const_class`

Fixes: https://github.com/dart-lang/sdk/issues/56880
Change-Id: I0f9399e74c3e07e3628d2bf3dcfbe0c21b7b9122
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/390060
Commit-Queue: Nicholas Shahan <nshahan@google.com>
Reviewed-by: Nate Biggs <natebiggs@google.com>

pkg/dev_compiler/test/hot_reload_suite.dart

diff --git a/pkg/dev_compiler/test/hot_reload_suite.dart b/pkg/dev_compiler/test/hot_reload_suite.dart
index 05eba1e..e66996c 100644
--- a/pkg/dev_compiler/test/hot_reload_suite.dart
+++ b/pkg/dev_compiler/test/hot_reload_suite.dart
@@ -13,6 +13,7 @@
 import 'package:dev_compiler/dev_compiler.dart' as ddc_names
     show libraryUriToJsIdentifier;
 import 'package:front_end/src/api_unstable/ddc.dart' as fe;
+import 'package:path/path.dart' as p;
 import 'package:reload_test/ddc_helpers.dart' as ddc_helpers;
 import 'package:reload_test/frontend_server_controller.dart';
 import 'package:reload_test/hot_reload_memory_filesystem.dart';
@@ -232,9 +233,10 @@
     // Report results for this test's sources' diff validations.
     void reportDiffOutcome(Uri fileUri, String testOutput, bool testPassed) {
       final filePath = fileUri.path;
+      final relativeFilePath = p.relative(filePath, from: allTestsUri.path);
       var outcome = TestResultOutcome(
         configuration: argResults['named-configuration'] as String,
-        testName: '$filePath-diff',
+        testName: '$relativeFilePath-diff',
         testOutput: testOutput,
       );
       outcome.elapsedTime = stopwatch.elapsed;

pkg/reload_test/lib/test_helpers.dart

diff --git a/pkg/reload_test/lib/test_helpers.dart b/pkg/reload_test/lib/test_helpers.dart
index a205399..ace1aed 100644
--- a/pkg/reload_test/lib/test_helpers.dart
+++ b/pkg/reload_test/lib/test_helpers.dart
@@ -18,7 +18,7 @@
 
   TestResultOutcome({
     required this.configuration,
-    this.suiteName = 'tests/reload',
+    this.suiteName = 'hot_reload',
     required this.testName,
     this.expectedResult = 'Pass',
     this.testOutput = '',