[LLDB][LLDB-DAP] Wire up DAP to listen to external progress events (llvm#123826)

Recently I added SBProgress (llvm#119052), and during that original commit I
tested if the progress event was sent over LLDB-DAP, and it was. However
upon the suggestion of @JDevlieghere and @labath we added an external
category (llvm#120171), which I did not test.

This small patch wires up DAP to listen for external events by default,
and adds the external category to the SBDebugger enumeration.

(cherry picked from commit b9813ce)

Author: Jlalond

lldb/tools/lldb-dap/lldb-dap.cpp

@@ -411,7 +411,8 @@ void SendStdOutStdErr(DAP &dap, lldb::SBProcess &process) {
 void ProgressEventThreadFunction(DAP &dap) {
   lldb::SBListener listener("lldb-dap.progress.listener");
   dap.debugger.GetBroadcaster().AddListener(
-      listener, lldb::SBDebugger::eBroadcastBitProgress);
+      listener, lldb::SBDebugger::eBroadcastBitProgress |
+                    lldb::SBDebugger::eBroadcastBitExternalProgress);
   dap.broadcaster.AddListener(listener, eBroadcastBitStopProgressThread);
   lldb::SBEvent event;
   bool done = false;