TouchpadInputMapper: add dump method

This dumps the state from the gesture converter, and a list of gesture
properties, which is useful for debugging settings.

Bug: 251196347
Test: run dumpsys input with touchpad connected, check output
Change-Id: I036d0251b06489b645b883a239ff345a98448497
diff --git a/services/inputflinger/reader/include/EventHub.h b/services/inputflinger/reader/include/EventHub.h
index a3ecf41..86acadb 100644
--- a/services/inputflinger/reader/include/EventHub.h
+++ b/services/inputflinger/reader/include/EventHub.h
@@ -19,6 +19,8 @@
 #include <bitset>
 #include <climits>
 #include <filesystem>
+#include <ostream>
+#include <string>
 #include <unordered_map>
 #include <utility>
 #include <vector>
@@ -77,6 +79,8 @@
     inline void clear() { *this = RawAbsoluteAxisInfo(); }
 };
 
+std::ostream& operator<<(std::ostream& out, const RawAbsoluteAxisInfo& info);
+
 /*
  * Input device classes.
  */