report: use consistent format for dumpEventTime

Use the same JS-compatible format on both POSIX and Windows.

PR-URL: #25751
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

Author: addaleax

src/node_report.cc

@@ -247,7 +247,7 @@ static void WriteNodeReport(Isolate* isolate,
 #ifdef _WIN32
   snprintf(timebuf,
            sizeof(timebuf),
-           "%4d/%02d/%02d %02d:%02d:%02d",
+           "%4d-%02d-%02dT%02d:%02d:%02dZ",
            tm_struct->wYear,
            tm_struct->wMonth,
            tm_struct->wDay,