[heap] Convert test-lab.cc -> lab-unittest.cc

Bug: v8:12781
Change-Id: I4cf23035a7679efdb4830335b75d8616abfbbe08
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3582385Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79958}

test/cctest/BUILD.gn

@@ -149,7 +149,6 @@ v8_source_set("cctest_sources") {
     "heap/test-incremental-marking.cc",
     "heap/test-invalidated-slots.cc",
     "heap/test-iterators.cc",
-    "heap/test-lab.cc",
     "heap/test-mark-compact.cc",
     "heap/test-memory-measurement.cc",
     "heap/test-page-promotion.cc",

test/unittests/BUILD.gn

@@ -329,6 +329,7 @@ v8_source_set("unittests_sources") {
     "heap/heap-utils.cc",
     "heap/heap-utils.h",
     "heap/index-generator-unittest.cc",
+    "heap/lab-unittest.cc",
     "heap/list-unittest.cc",
     "heap/local-factory-unittest.cc",
     "heap/local-heap-unittest.cc",