Introduce feature flag for UiAutomation inject event test/hidden APIs

UiAutomation#injectInputEvent and
UiAutomation#injectInputEventToInputFilter hidden/test API should be
deprecate in favor of UinputDevice, HidDevice, and InjectInputInProcess
for in-process input event injection.

Flag: com.android.input.flags.deprecate_uiautomation_input_injection
Test: m
Bug: 277261245

Change-Id: I4b7aacbb842b2e970df60669ef172a293dc8d04c
diff --git a/libs/input/input_flags.aconfig b/libs/input/input_flags.aconfig
index bf928f4..f17575d 100644
--- a/libs/input/input_flags.aconfig
+++ b/libs/input/input_flags.aconfig
@@ -244,3 +244,11 @@
     purpose: PURPOSE_BUGFIX
   }
 }
+
+flag {
+  name: "deprecate_uiautomation_input_injection"
+  namespace: "input"
+  description: "Deprecate UiAutomation#injectInputEvent and UiAutomation#injectInputEventToInputFilter test/hidden APIs"
+  bug: "277261245"
+}
+