Add normalization for thread IDs in panic messages

So we don't need to add normalization to every test that includes a
panic message, add a global normalization to compiletest.

src/tools/compiletest/src/runtest.rs

@@ -2567,6 +2567,11 @@ impl<'test> TestCx<'test> {
                 })
                 .into_owned();
 
+        // Normalize thread IDs in panic messages
+        normalized = static_regex!(r"thread '(?P<name>.*?)' \((rtid )?\d+\) panicked")
+            .replace_all(&normalized, "thread '$name' ($$TID) panicked")
+            .into_owned();
+
         normalized = normalized.replace("\t", "\\t"); // makes tabs visible
 
         // Remove test annotations like `//~ ERROR text` from the output,

src/tools/miri/tests/ui.rs

@@ -248,7 +248,8 @@ regexes! {
     // erase alloc ids
     "alloc[0-9]+"                    => "ALLOC",
     // erase thread ids
-    r"unnamed-[0-9]+"               => "unnamed-ID",
+    r"unnamed-[0-9]+"                => "unnamed-ID",
+    r"thread '(?P<name>.*?)' \(\d+\) panicked" => "thread '$name' ($$TID) panicked",
     // erase borrow tags
     "<[0-9]+>"                       => "<TAG>",
     "<[0-9]+="                       => "<TAG=",