[LLDB][Platform Linux] Flip uid and pid in get signal description (#142200)

Despite a great review from @labath, I accidentally landed the signal
with the UID and PID properties flipped. I was actually trying to write
tests for this feature when I discovered it.

This fixes that bug, and add a shell test that runs only on Nix systems.

lldb/source/Plugins/Platform/Linux/PlatformLinux.cpp

@@ -580,7 +580,7 @@ static std::string GetDescriptionFromSiginfo(lldb::ValueObjectSP siginfo_sp) {
   }
 
   return linux_signals.GetSignalDescription(signo, code, addr, lower, upper,
-                                            uid, pid);
+                                            pid, uid);
 }
 
 lldb::StopInfoSP PlatformLinux::GetStopInfoFromSiginfo(Thread &thread) {

lldb/test/Shell/Register/Core/Inputs/tkill.cpp

@@ -0,0 +1,10 @@
+#include <signal.h>
+#include <sys/syscall.h>
+
+int main() {
+  // Get the current thread ID
+  pid_t tid = syscall(SYS_gettid);
+  // Send a SIGSEGV signal to the current thread
+  syscall(SYS_tkill, tid, SIGSEGV);
+  return 0;
+}

lldb/test/Shell/Register/Core/x86-64-linux-tkill.test

@@ -0,0 +1,5 @@
+# REQUIRES: system-linux
+# RUN: %lldb -b -s %s -c %p/Inputs/x86-64-linux-tkill.core | FileCheck %s
+
+thread list
+# CHECK: hread #1: tid = 2667987, 0x00007f9a265076cd, name = 'tkill.out', stop reason = SIGSEGV: sent by tkill system call (sender pid=2667987, uid=649752)