[test] Run test262 on fyi bots.

Bug: v8:6917
Change-Id: I45ef97a2756f438f03f5d961381624e477680dee
Reviewed-on: https://chromium-review.googlesource.com/866497Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michał Majewski <majeski@google.com>
Cr-Commit-Position: refs/heads/master@{#50604}

infra/testing/client.v8.pyl

@@ -35,11 +35,13 @@
   ],
   'V8 Linux64 - fyi': [
     {'name': 'v8testing', 'variant': 'infra_staging', 'shards': 1},
+    {'name': 'test262_variants', 'variant': 'infra_staging', 'shards': 2},
     {'name': 'mjsunit', 'variant': 'stress_sampling', 'shards': 1},
     {'name': 'webkit', 'variant': 'stress_sampling', 'shards': 1},
   ],
   'V8 Linux64 - debug - fyi': [
     {'name': 'v8testing', 'variant': 'infra_staging', 'shards': 2},
+    {'name': 'test262_variants', 'variant': 'infra_staging', 'shards': 3},
     {'name': 'mjsunit', 'variant': 'stress_sampling', 'shards': 1},
     {'name': 'webkit', 'variant': 'stress_sampling', 'shards': 1},
   ],

infra/testing/tryserver.v8.pyl

@@ -10,6 +10,7 @@
 
   'v8_linux64_fyi_rel_ng_triggered': [
     {'name': 'v8testing', 'variant': 'infra_staging', 'shards': 2},
+    {'name': 'test262_variants', 'variant': 'infra_staging', 'shards': 2},
     {'name': 'mjsunit', 'variant': 'stress_sampling', 'shards': 1},
     {'name': 'webkit', 'variant': 'stress_sampling', 'shards': 1},
   ],