[asan] Remove the use of system properties on Android.

System properties are not accessible through NDK (we've been using
hacks to get to them) and they are unavailable during ASan
initialization in .preinit_array. Use environment variables and
files instead (ex. ASAN_OPTIONS=include_if_exists=/path).

No test changes. This feature was not tested because the properties
are system-wide and would conflict with the parallel test runner. Yet
another reason to get rid of it.

llvm-svn: 254783