[Sanitizer] Introduce SANITIZER_CAN_USE_PREINIT_ARRAY definition and use it across sanitizers.

Get rid of ASAN_USE_PREINIT_ARRAY and LSAN_USE_PREINIT_ARRAY - just always
use .preinit_array if it's available. This mode seems stable enough, and
we've been relying on default values of these macro for a long time.

llvm-svn: 213980