profiling: factor callstack trie out into p/common/

+ leftovers from previous traced_perf review

Bug: 144281346
Change-Id: I74a8e7da9e9d66423dcfbf4edde02325b067959a
diff --git a/gn/perfetto_unittests.gni b/gn/perfetto_unittests.gni
index 84467e6..aae3085 100644
--- a/gn/perfetto_unittests.gni
+++ b/gn/perfetto_unittests.gni
@@ -57,6 +57,10 @@
   ]
 }
 
+if (enable_perfetto_heapprofd || enable_perfetto_traced_perf) {
+  perfetto_unittests_targets += [ "src/profiling/common:unittests" ]
+}
+
 if (enable_perfetto_heapprofd) {
   perfetto_unittests_targets += [
     "src/profiling/memory:unittests",