Auto merge of #29346 - mrobinson:aggregate-unexpected-logs, r=delan

Aggregate unexpected results into logs

This makes it easier to run `update-wpt` based on results from the bots by writing a new version of the raw log that filters out all tests with expected results.  Then aggregate this output into the filtered results archive. A future version of this could aggregate all unexpected results that were not filtered as intermittents.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes do not require tests because they are infrastructure changes.

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python/servo/testing_commands.py

@@ -87,6 +87,9 @@ def create_parser_wpt():
     parser.add_argument('--filter-intermittents', default=None, action="store",
                         help="Filter intermittents against known intermittents "
                              "and save the filtered output to the given file.")
+    parser.add_argument('--log-raw-unexpected', default=None, action="store",
+                        help="Raw structured log messages for unexpected results."
+                             " '--log-raw' Must also be passed in order to use this.")
     return parser