Error Prone for RequiresPermission across AIDL.

We've had @RequiresPermission annotations across public APIs for many
years, but we've never built out the tooling to validate that the
service implementations actually enforced those permissions.

This change adds an Error Prone checker that does bi-directional
validation of these annotations, confirming that AIDL implementations
enforce the permissions, and that AIDL callers carry those
annotations through any indirect call-paths.

Currently, enforcement validation is best-effort, since it assumes
that any enforcement referencing the annotated permissions is enough
to pass; it doesn't attempt any code flow analysis.  It also doesn't
understand concepts like Binder.clearCallingIdentity().

To begin using this checker, simply begin annotating your AIDL files
using a strategy like this:

    @JavaPassthrough(annotation="@android.annotation.RequiresPermission(android.Manifest.permission.BLUETOOTH_PRIVILEGED)")
    void aidlMethod();

Bug: 183626724
Test: atest error_prone_android_framework_test:RequiresPermissionCheckerTest
Change-Id: I26a872f07ab13931c241cbb02ff7228edf7dc3b9