[test] Move cctest/test-elements-kind to unittests

... /objects/elements-kind-unittest.

Bug: v8:12781
Change-Id: I335cec050faf584652a43041437ec0a14539cf1e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3607115Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: 王澳 <wangao.james@bytedance.com>
Cr-Commit-Position: refs/heads/main@{#80553}

test/cctest/BUILD.gn

@@ -208,7 +208,6 @@ v8_source_set("cctest_sources") {
     "test-diy-fp.cc",
     "test-double.cc",
     "test-dtoa.cc",
-    "test-elements-kind.cc",
     "test-factory.cc",
     "test-fast-dtoa.cc",
     "test-feedback-vector.cc",

test/unittests/BUILD.gn

@@ -388,6 +388,7 @@ v8_source_set("unittests_sources") {
     "objects/concurrent-script-context-table-unittest.cc",
     "objects/concurrent-string-unittest.cc",
     "objects/concurrent-transition-array-unittest.cc",
+    "objects/elements-kind-unittest.cc",
     "objects/modules-unittest.cc",
     "objects/object-unittest.cc",
     "objects/swiss-hash-table-helpers-unittest.cc",