[lldb] Add missing return statements in ThreadMemory (llvm#126128)

These prevented ThreadMemory from correctly returning the
Name/Queue/Info of the backing thread.

Note about testing: this test only finds regressions if the system sets
a name or queue for the backing thread. While this may not be true
everywhere, it still provides coverage in some systems, e.g. in Apple
platforms.

(cherry picked from commit b800293)

Author: felipepiovezan

lldb/source/Plugins/Process/Utility/ThreadMemory.h

@@ -33,23 +33,23 @@ class ThreadMemory : public lldb_private::Thread {
 
   const char *GetInfo() override {
     if (m_backing_thread_sp)
-      m_backing_thread_sp->GetInfo();
+      return m_backing_thread_sp->GetInfo();
     return nullptr;
   }
 
   const char *GetName() override {
     if (!m_name.empty())
       return m_name.c_str();
     if (m_backing_thread_sp)
-      m_backing_thread_sp->GetName();
+      return m_backing_thread_sp->GetName();
     return nullptr;
   }
 
   const char *GetQueueName() override {
     if (!m_queue.empty())
       return m_queue.c_str();
     if (m_backing_thread_sp)
-      m_backing_thread_sp->GetQueueName();
+      return m_backing_thread_sp->GetQueueName();
     return nullptr;
   }
 

lldb/test/API/functionalities/plugins/python_os_plugin/TestPythonOSPlugin.py

@@ -160,6 +160,8 @@ def run_python_os_step(self):
         )
         self.assertTrue(process, PROCESS_IS_VALID)
 
+        core_thread_zero = process.GetThreadAtIndex(0)
+
         # Make sure there are no OS plug-in created thread when we first stop
         # at our breakpoint in main
         thread = process.GetThreadByID(0x111111111)
@@ -183,6 +185,10 @@ def run_python_os_step(self):
             thread.IsValid(),
             "Make sure there is a thread 0x111111111 after we load the python OS plug-in",
         )
+        # This OS plugin does not set thread names / queue names, so it should
+        # inherit the core thread's name.
+        self.assertEqual(core_thread_zero.GetName(), thread.GetName())
+        self.assertEqual(core_thread_zero.GetQueueName(), thread.GetQueueName())
 
         frame = thread.GetFrameAtIndex(0)
         self.assertTrue(