Adjust LDBG output: surround DebugType between [ and ] (#150671)

This makes the output more readable by clearly showing the current debug
type as a keyword.

Author: joker-eph

llvm/include/llvm/Support/DebugLog.h

@@ -38,8 +38,8 @@ class LogWithNewline {
                  raw_ostream &os)
       : os(os) {
     if (debug_type)
-      os << debug_type << " ";
-    os << "[" << file << ":" << line << "] ";
+      os << "[" << debug_type << "] ";
+    os << file << ":" << line << " ";
   }
   ~LogWithNewline() { os << '\n'; }
   template <typename T> raw_ostream &operator<<(const T &t) && {