InputTracer: Add tests for perfetto backend

Add a new InputTraceSession class that encapsulates the logic to take
and decode a perfetto input trace for testing.

Then, use it to add new tests to verify the behavior of entire tracing
framework, using InputDispatcher as the interface.

Bug: 210460522
Test: atest inputflinger_tests
Change-Id: I5a9b47e831c5c30e5d7f2b60c9b8075b7d330e9e
diff --git a/services/inputflinger/tests/FakeInputDispatcherPolicy.h b/services/inputflinger/tests/FakeInputDispatcherPolicy.h
index d83924f..2cc018e 100644
--- a/services/inputflinger/tests/FakeInputDispatcherPolicy.h
+++ b/services/inputflinger/tests/FakeInputDispatcherPolicy.h
@@ -115,6 +115,7 @@
     void setUnhandledKeyHandler(std::function<std::optional<KeyEvent>(const KeyEvent&)> handler);
     void assertUnhandledKeyReported(int32_t keycode);
     void assertUnhandledKeyNotReported();
+    void addPackageUidMapping(std::string package, gui::Uid uid);
 
 private:
     std::mutex mLock;
@@ -150,6 +151,8 @@
     std::queue<int32_t> mReportedUnhandledKeycodes GUARDED_BY(mLock);
     std::function<std::optional<KeyEvent>(const KeyEvent&)> mUnhandledKeyHandler GUARDED_BY(mLock);
 
+    std::map<std::string, gui::Uid> mPackageUidMap GUARDED_BY(mLock);
+
     /**
      * All three ANR-related callbacks behave the same way, so we use this generic function to wait
      * for a specific container to become non-empty. When the container is non-empty, return the