[test] Move cctest/test-identity-map to unittests/

... utils/identity-map-unittest.

Bug: v8:12781
Change-Id: I875de2b1e589ec72d724a6d0745a5d615344b510
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3724792Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: 王澳 <wangao.james@bytedance.com>
Cr-Commit-Position: refs/heads/main@{#81531}

test/cctest/BUILD.gn

@@ -188,7 +188,6 @@ v8_source_set("cctest_sources") {
     "test-global-handles.cc",
     "test-heap-profiler.cc",
     "test-icache.cc",
-    "test-identity-map.cc",
     "test-ignition-statistics-extension.cc",
     "test-inobject-slack-tracking.cc",
     "test-inspector.cc",

test/unittests/BUILD.gn

@@ -472,6 +472,7 @@ v8_source_set("unittests_sources") {
     "utils/allocation-unittest.cc",
     "utils/bit-vector-unittest.cc",
     "utils/detachable-vector-unittest.cc",
+    "utils/identity-map-unittest.cc",
     "utils/locked-queue-unittest.cc",
     "utils/sparse-bit-vector-unittest.cc",
     "utils/utils-unittest.cc",