Print errors during stdlib testing (#16128)

# Description
This PR adds error output display for stdlib tests. This makes it easier
to understand why a test is failing. Here's what an example error output
looks like:


![image](https://github.com/user-attachments/assets/ed06b53e-c3f9-4c56-a646-7e6486ce7ec6)


# User-Facing Changes
N/A

# Tests + Formatting
N/A

# After Submitting
N/A

crates/nu-std/testing.nu

@@ -240,13 +240,15 @@ def run-tests-for-module [
             log info $"Running ($test.test) in module ($module.name)"
             log debug $"Global context is ($global_context)"
 
-            $test|insert result {|x|
-                run-test $test $plugins
-                | if $in.exit_code == 0 {
-                    'pass'
-                } else {
-                    'fail'
-                }
+            $test | insert result { run-test $test $plugins }
+        }
+        | collect # Avoid interleaving errors
+        | update result {|test|
+            if $in.exit_code == 0 {
+                'pass'
+            } else {
+                log error $"Error while running ($test.test) in module ($module.name)(char nl)($in.stderr)"
+                'fail'
             }
         }
         | append $skipped_tests