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/mapper/TouchpadInputMapper.h b/services/inputflinger/reader/mapper/TouchpadInputMapper.h
index 8ffc8a0..d693bca 100644
--- a/services/inputflinger/reader/mapper/TouchpadInputMapper.h
+++ b/services/inputflinger/reader/mapper/TouchpadInputMapper.h
@@ -41,6 +41,8 @@
     ~TouchpadInputMapper();
 
     uint32_t getSources() const override;
+    void dump(std::string& dump) override;
+
     [[nodiscard]] std::list<NotifyArgs> configure(nsecs_t when,
                                                   const InputReaderConfiguration* config,
                                                   uint32_t changes) override;