Add disabled test which generates huge output into JUnit file

tests/report/junit/data/main.fmf

@@ -32,6 +32,20 @@
         /escape"<speci&l>_chars:
             test: ./special_chars.sh
 
+        /big-output:
+            summary: Generate huge text data into <system-out> JUnit tag
+            link:
+              - verifies: https://github.com/teemtee/tmt/issues/3363
+            require:
+              - python
+
+            # The test must fail to generate output into a <system-out> tag
+            result: fail
+            test: python -c "print('a' * (10 * 1024 * 1024 + 1))"
+
+            # Do not enable the test by default to not waste the CI resources
+            enabled: false
+
         /subresults/pass:
             summary: Basic pass test of shell subresults
             test: |