test: run doctool tests in parallel

PR-URL: #47273
Refs: #47146
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: joyeecheung

test/doctool/testcfg.py

@@ -4,4 +4,4 @@
 import testpy
 
 def GetConfiguration(context, root):
-    return testpy.SimpleTestConfiguration(context, root, 'doctool')
+    return testpy.ParallelTestConfiguration(context, root, 'doctool')