[CQ] Experiment to speed up the debug builder

No-Try: true
Bug: v8:11428
Change-Id: Ib5ccee00f1e010f94a9d504478553dd47a2998a0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3557252Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79660}

infra/testing/builders.pyl

@@ -347,15 +347,15 @@
       'os': 'Ubuntu-18.04',
     },
     'tests': [
-      {'name': 'benchmarks'},
+      {'name': 'benchmarks', 'shards': 2},
       {'name': 'benchmarks', 'variant': 'extra'},
-      {'name': 'mjsunit_sp_frame_access'},
+      {'name': 'mjsunit_sp_frame_access', 'shards': 2},
       {'name': 'mozilla'},
       {'name': 'mozilla', 'variant': 'extra'},
-      {'name': 'test262', 'variant': 'default'},
-      {'name': 'test262', 'variant': 'extra', 'shards': 5},
-      {'name': 'v8testing', 'shards': 3},
-      {'name': 'v8testing', 'variant': 'extra', 'shards': 3},
+      {'name': 'test262', 'variant': 'default', 'shards': 2},
+      {'name': 'test262', 'variant': 'extra', 'shards': 9},
+      {'name': 'v8testing', 'shards': 5},
+      {'name': 'v8testing', 'variant': 'extra', 'shards': 5},
       {'name': 'v8testing', 'variant': 'minor_mc'},
       {'name': 'v8testing', 'variant': 'no_lfa'},
       {'name': 'v8testing', 'variant': 'stress_instruction_scheduling'},