test_runner: enhance #handleEvent to handle diagnostic levels

Updated  to process the  parameter for
 events. Messages are now formatted with
colors based on the  (e.g., 'info', 'warn',
'error').

This change ensures diagnostic messages are visually distinct,
improving clarity and reducing debugging effort during test runs.

Refs: nodejs#55922

lib/internal/test_runner/reporter/spec.js

@@ -69,8 +69,10 @@ class SpecReporter extends Transform {
       case 'test:stderr':
       case 'test:stdout':
         return data.message;
-      case 'test:diagnostic':
-        return `${reporterColorMap[type]}${indent(data.nesting)}${reporterUnicodeSymbolMap[type]}${data.message}${colors.white}\n`;
+      case 'test:diagnostic':{
+        const diagnosticColor = reporterColorMap[data.level] || reporterColorMap['test:diagnostic'];
+        return `${diagnosticColor}${indent(data.nesting)}${reporterUnicodeSymbolMap[type]}${data.message}${colors.white}\n`;
+      }
       case 'test:coverage':
         return getCoverageReport(indent(data.nesting), data.summary,
                                  reporterUnicodeSymbolMap['test:coverage'], colors.blue, true);