libutils: introduce sp<T>::make

This is in preparation of doing what we did for SharedRefBase (hiding
operator new) so that clients can't accidentally construct
shared_ptr/unique_ptr or any other alternative memory management scheme
which would conflict with RefBase. You can see what ultimately happened
to SharedRefBase in frameworks/native CL
10d9ddf2e3da3ba3a425fb8396aaaec728e5fbdb.

The goal for this:
- promote use of 'sp<T>::make' over 'sp<T> .. = new T'
- make 'operator new' a private member of RefBase

Bug: 138956784
Test: libutils_test
Change-Id: I47f4d28edbf7534730c7b6fb1de748dd60f34e11
diff --git a/libutils/StrongPointer_test.cpp b/libutils/StrongPointer_test.cpp
index 7b2e37f..d37c1de 100644
--- a/libutils/StrongPointer_test.cpp
+++ b/libutils/StrongPointer_test.cpp
@@ -36,10 +36,8 @@
 
 TEST(StrongPointer, move) {
     bool isDeleted;
-    SPFoo* foo = new SPFoo(&isDeleted);
-    ASSERT_EQ(0, foo->getStrongCount());
-    ASSERT_FALSE(isDeleted) << "Already deleted...?";
-    sp<SPFoo> sp1(foo);
+    sp<SPFoo> sp1 = sp<SPFoo>::make(&isDeleted);
+    SPFoo* foo = sp1.get();
     ASSERT_EQ(1, foo->getStrongCount());
     {
         sp<SPFoo> sp2 = std::move(sp1);
@@ -65,7 +63,7 @@
 
 TEST(StrongPointer, PointerComparison) {
     bool isDeleted;
-    sp<SPFoo> foo = new SPFoo(&isDeleted);
+    sp<SPFoo> foo = sp<SPFoo>::make(&isDeleted);
     ASSERT_EQ(foo.get(), foo);
     ASSERT_EQ(foo, foo.get());
     ASSERT_NE(nullptr, foo);