Replace the "--verbose" flag with "-wW" when invoking the test

suite, so that the tests are run in non-verbose mode by default and
failed tests are rerun in verbose mode.

Also add the "--slowest" flag when invoking the test suite to
list the ten slowest tests at the end of the test run.

python3.spec

@@ -1155,7 +1155,7 @@ CheckPython() {
   #   aarch64, see upstream bug http://bugs.python.org/issue21131
   WITHIN_PYTHON_RPM_BUILD= \
   LD_LIBRARY_PATH=$ConfDir $ConfDir/python -m test.regrtest \
-    --verbose --findleaks \
+    -wW --slowest --findleaks \
     -x test_distutils \
     %ifarch ppc64le aarch64
     -x test_faulthandler \