Use std::filesystem for input event devices scan.

Use std::filesystem directory iterator to scan event devices in EventHub.

Bug: 160010896
Test: atest inputflinger_tests, atest EventHubTest
Change-Id: Ib5658e96783b8a1099fe0a2cb6dda51703045c84
diff --git a/services/inputflinger/reader/Android.bp b/services/inputflinger/reader/Android.bp
index 83a610f..0ccada9 100644
--- a/services/inputflinger/reader/Android.bp
+++ b/services/inputflinger/reader/Android.bp
@@ -81,4 +81,7 @@
     export_header_lib_headers: [
         "libinputreader_headers",
     ],
+    static_libs: [
+        "libc++fs"
+    ],
 }