frameworks/base: switch to using NativeConstants.

NativeCrypto is a conscrypt class that contained several OpenSSL
constants. NativeConstants is the new class that contains the same
thing, but the latter is automatically generated and thus won't drift
from the C headers.

Bug: 20521989

Change-Id: I45c7b9a6844a06e3ffd09be692ebf733e1ebbbcc