Implement KeyboardClassifier interface in rust

DD: go/project-imposter-android
This CL includes:
- Rust interface setup

Next CL to include:
- Basic categorization into alphabetic and non-alphabetic
- Updating categorization based on key presses

Test: atest --host libinput_rust_test
Test: atest inputflinger_tests
Bug: 263559234
Flag: com.android.input.flags.enable_keyboard_classifier_rust_impl
Change-Id: I52773be992ddd8efaa9546e0af8b0a78515d931c
diff --git a/services/inputflinger/reader/include/InputReaderContext.h b/services/inputflinger/reader/include/InputReaderContext.h
index 907a49f..e0e0ac2 100644
--- a/services/inputflinger/reader/include/InputReaderContext.h
+++ b/services/inputflinger/reader/include/InputReaderContext.h
@@ -17,6 +17,7 @@
 #pragma once
 
 #include <input/InputDevice.h>
+#include <input/KeyboardClassifier.h>
 #include "NotifyArgs.h"
 
 #include <vector>
@@ -64,6 +65,8 @@
 
     virtual void setLastKeyDownTimestamp(nsecs_t when) = 0;
     virtual nsecs_t getLastKeyDownTimestamp() = 0;
+
+    virtual KeyboardClassifier& getKeyboardClassifier() = 0;
 };
 
 } // namespace android