test: address flaky wpt/test-timers

Moving test harness from Parallel to Simple resolves most of the
failures. negative-settimeout.any.js still needs to be marked flaky.

Refs: #37672

PR-URL: #37691
Fixes: #37672
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>

Author: Trott

test/wpt/status/html/webappapis/timers.json

@@ -1 +1,5 @@
-{}
+{
+  "negative-settimeout.any.js": {
+    "fail": "unreliable in Node.js; Refs: https://github.com/nodejs/node/issues/37672"
+  }
+}

test/wpt/testcfg.py

@@ -3,4 +3,4 @@
 import testpy
 
 def GetConfiguration(context, root):
-  return testpy.ParallelTestConfiguration(context, root, 'wpt')
+  return testpy.SimpleTestConfiguration(context, root, 'wpt')