[vscode] fix ubsan problem in the progress event reporter

[wallace]

Summary

The error

UndefinedBehaviorSanitizer: undefined-behavior /Users/buildslave/jenkins/workspace/lldb-cmake-sanitized/llvm-project/lldb/tools/lldb-vscode/ProgressEvent.cpp:89:64 in

was found in https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake-sanitized/1910/consoleFull#-15641370498254eaf0-7326-4999-85b0-388101f2d404

It turns out that we were not setting m_event_type when initializatin
and update case. The fix is very simple.

lldb/tools/lldb-vscode/ProgressEvent.cpp

if (completed == 0) {
     // End event
     m_event_type = progressEnd;
     // We should report the end event right away.
     m_minimum_allowed_report_time = std::chrono::seconds::zero();
     if (calculate_percentage)
       m_percentage = 100;
   } else {
     // Update event
+    m_event_type = progressUpdate;
     m_percentage = std::min(
         (uint32_t)((double)completed / (double)total * 100.0), (uint32_t)99);
     if (prev_event->Reported()) {
       // Add a small delay between reports
       m_minimum_allowed_report_time =
           prev_event->m_minimum_allowed_report_time +
           kUpdateProgressEventReportDelay;
     } else {