Convert tool type to enum class

For better type safety, use enum class when sending tool type.

Bug: 198472780
Test: atest libinput_tests inputflinger_tests
Change-Id: I371f08087b9513b6f75966c124de77bc12f8324e
diff --git a/services/inputflinger/reader/include/StylusState.h b/services/inputflinger/reader/include/StylusState.h
index ff15e0c..d042784 100644
--- a/services/inputflinger/reader/include/StylusState.h
+++ b/services/inputflinger/reader/include/StylusState.h
@@ -33,8 +33,8 @@
     std::optional<float> pressure{};
     /* The state of the stylus buttons as a bitfield (e.g. AMOTION_EVENT_BUTTON_SECONDARY). */
     uint32_t buttons{};
-    /* Which tool type the stylus is currently using (e.g. AMOTION_EVENT_TOOL_TYPE_ERASER). */
-    int32_t toolType{AMOTION_EVENT_TOOL_TYPE_UNKNOWN};
+    /* Which tool type the stylus is currently using (e.g. ToolType::ERASER). */
+    ToolType toolType{ToolType::UNKNOWN};
 
     void clear() { *this = StylusState{}; }
 };