Open FIS/FOS through common IoBridge code.

To support legacy apps that are using "_data" columns via public APIs,
we're looking at a design that requires hooking of all open(2) calls
performed in Java.

Upstream FileInputStream and FileOutputStream use their own native
code to open files, so this change modifies them to instead use
IoBridge to open their FileDescriptors, which enables the hooking
described above.

Since IoBridge indirectly applies BlockGuard policy, we no longer
need to trigger it explicitly in FIS/FOS.

Update tests to reflect BlockGuard violations, with notes about
why each is triggered.  Also add tests for RandomAccessFile.

Bug: 111268862, 111960973
Test: cts-tradefed run singleCommand cts-dev -a arm64-v8a -m CtsLibcoreTestCases -t libcore.dalvik.system.BlockGuardTest
Change-Id: I018a50950d37385470574ff312bdd12d4f0c3525