[CD Cursor] Devopts override for connected displays flag

Add and use a sysprop based override for connected displays cursor flag.
Override is expected to require an restart on change. Allowing us to
cache its value.

Test: atest inputflinger_tests
Bug: 362719483
Flag: com.android.input.flags.connected_displays_cursor

Change-Id: I8634e61eb57c82b2b4c904239a4d407ce69f97d8
diff --git a/libs/input/Android.bp b/libs/input/Android.bp
index d2e4320..ff26184 100644
--- a/libs/input/Android.bp
+++ b/libs/input/Android.bp
@@ -230,6 +230,7 @@
         "InputConsumerNoResampling.cpp",
         "InputDevice.cpp",
         "InputEventLabels.cpp",
+        "InputFlags.cpp",
         "InputTransport.cpp",
         "InputVerifier.cpp",
         "KeyCharacterMap.cpp",