[build] Add new trybots to CQ experiment

NOTRY=true
TBR=sergiyb@chromium.org

Bug: v8:6918
Change-Id: I16d44acd8c5cf57d472e4e8ffebf08b3d316441c
Reviewed-on: https://chromium-review.googlesource.com/720370Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48573}

infra/config/cq.cfg

@@ -80,6 +80,10 @@ verifiers {
         name: "v8_linux_rel_ng_triggered"
         triggered_by: "v8_linux_rel_ng"
       }
+      builders {
+        name: "v8_linux_shared_compile_rel"
+        experiment_percentage: 20
+      }
       builders { name: "v8_linux_verify_csa_rel_ng" }
       builders {
         name: "v8_linux_verify_csa_rel_ng_triggered"
@@ -107,6 +111,10 @@ verifiers {
         name: "v8_win_rel_ng_triggered"
         triggered_by: "v8_win_rel_ng"
       }
+      builders {
+        name: "v8_win64_clang_compile_rel"
+        experiment_percentage: 20
+      }
       builders {
         name: "v8_linux_blink_rel"
         experiment_percentage: 100