KAFKA-17418: Improve markdown formatting in junit.py (apache#17071)

Newline characters in the failure message of tests were causing the Markdown tables to be malformed.
This patch fixes that by replacing newlines with "<br>" tags and escaping other HTML that may appear in message.

Reviewers: David Arthur <mumrah@gmail.com>

.github/scripts/junit.py

@@ -23,6 +23,7 @@
 import sys
 from typing import Tuple, Optional, List, Iterable
 import xml.etree.ElementTree
+import html
 
 
 logger = logging.getLogger()
@@ -99,6 +100,9 @@ def parse_report(workspace_path, report_path, fp) -> Iterable[TestSuite]:
                 test_case_failed = False
             elif elem.tag == "failure":
                 failure_message = elem.get("message")
+                if failure_message:
+                    failure_message = html.escape(failure_message)
+                    failure_message = failure_message.replace('\n', '<br>').replace('\r', '<br>')
                 failure_class = elem.get("type")
                 failure_stack_trace = elem.text
                 failure = partial_test_case(failure_message, failure_class, failure_stack_trace)