Extract FakeInputDispatcherPolicy into a separate cpp file

It will be used by other tests that will be added in the future.

Bug: 210460522
Test: build
Change-Id: I36d6b5aef98e621d8193d72063e8c7ecddd567a3
diff --git a/services/inputflinger/tests/fuzzers/Android.bp b/services/inputflinger/tests/fuzzers/Android.bp
index 81c3353..48e1954 100644
--- a/services/inputflinger/tests/fuzzers/Android.bp
+++ b/services/inputflinger/tests/fuzzers/Android.bp
@@ -178,7 +178,12 @@
     shared_libs: [
         "libinputreporter",
     ],
+    static_libs: [
+        "libgmock",
+        "libgtest",
+    ],
     srcs: [
+        ":inputdispatcher_common_test_sources",
         "InputDispatcherFuzzer.cpp",
     ],
 }