oeqa/core/runner: stub addDuration in OETestResult

We have a custom TestResult implementation, and Python 3.12 added a new
method addDuration() to the TestResult interface.  This would be useful
to implement correctly, but for now stub it out to silence the warning
when running under Python 3.12:

/usr/lib64/python3.12/unittest/case.py:580: RuntimeWarning: TestResult has no addDuration method
  warnings.warn("TestResult has no addDuration method",

(From OE-Core rev: 9105e2bbf3245bfa02d2f4c55a010a7d2c3da6c2)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 2d6fff81b34476b890f6943997615fbf8d3d133f)
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Paul Barker <paul@pbarker.dev>

meta/lib/oeqa/core/runner.py

@@ -78,6 +78,10 @@ class OETestResult(_TestResult):
                     self.shownmsg.append(test.id())
                     break
 
+    # Python 3.12 added this, stub it out for now
+    def addDuration(self, test, elapsed):
+         pass
+
     def logSummary(self, component, context_msg=''):
         elapsed_time = self.tc._run_end_time - self.tc._run_start_time
         self.tc.logger.info("SUMMARY:")