[lldb-dap] Avoid double 'new' events for dyld on Darwin (llvm#140810)

I got a bug report where a pedantic DAP client complains about getting
two "new" module events for the same UUID. This is caused by the dyld
transition from the on-disk dyld to the shared cache dyld, which share
the same UUID. The transition is not generating an unloaded event
(because we're not really unloading dyld) but we do get a loaded event
(because the load address changed). This PR fixes the issue by relying
on the modules set as the source of truth instead of relying on the
event type.

Back-ported from commit 7b51339

Author: JDevlieghere

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

@@ -540,22 +540,17 @@ void EventThreadFunction(DAP &dap) {
 
             llvm::StringRef reason;
             bool id_only = false;
-            if (event_mask & lldb::SBTarget::eBroadcastBitModulesLoaded) {
-              dap.modules.insert(module_id);
-              reason = "new";
-            } else {
-              // If this is a module we've never told the client about, don't
-              // send an event.
-              if (!dap.modules.contains(module_id))
-                continue;
-
+            if (dap.modules.contains(module_id)) {
               if (event_mask & lldb::SBTarget::eBroadcastBitModulesUnloaded) {
                 dap.modules.erase(module_id);
                 reason = "removed";
                 id_only = true;
               } else {
                 reason = "changed";
               }
+            } else {
+              dap.modules.insert(module_id);
+              reason = "new";
             }
 
             llvm::json::Object body;