cppgc: Migrate workload tests

Bug: chromium:1056170
Change-Id: I78844ed1921c5558a2c5ab6121208c1887fe8b3f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2826118
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73961}

test/unittests/BUILD.gn

@@ -130,6 +130,7 @@ v8_source_set("cppgc_unittests_sources") {
     "heap/cppgc/tests.h",
     "heap/cppgc/visitor-unittest.cc",
     "heap/cppgc/weak-container-unittest.cc",
+    "heap/cppgc/workloads-unittest.cc",
     "heap/cppgc/write-barrier-unittest.cc",
   ]