libutils: RefBase always disallow on stack

Before, we only did this in sp<> constructors, but we can always make
this check during the initial incStrong.

Since prebuilts call into the existing report race function declared
in StrongPointer.h, we still call this function from RefBase.cpp.

Bug: 232557259
Test: libutils_test
Change-Id: I4080b1869b83ecf655fc9c182b6de768a6358adf