bpo-30263: regrtest: log system load (#1452)

* bpo-30263: regrtest: log system load

* regrtest: log the number of CPUs

Log the number of CPUs in the header. --verbose now imply --header.
diff --git a/Lib/test/libregrtest/cmdline.py b/Lib/test/libregrtest/cmdline.py
index d621f5f..8260b09 100644
--- a/Lib/test/libregrtest/cmdline.py
+++ b/Lib/test/libregrtest/cmdline.py
@@ -343,5 +343,7 @@
                     ns.use_resources.append(r)
     if ns.random_seed is not None:
         ns.randomize = True
+    if ns.verbose:
+        ns.header = True
 
     return ns