Add new flag for exposing 1.4 instance API

Bug: b/370568136
Flag: com.android.graphics.libvulkan.flags.vulkan_1_4_instance_api
Change-Id: Ib259225055c536669d134479634ad5a9289c755d

Author: chrisforbes

vulkan/libvulkan/libvulkan_flags.aconfig

@@ -8,3 +8,11 @@ flag {
   bug: "341978292"
   is_fixed_read_only: true
 }
+
+flag {
+  name: "vulkan_1_4_instance_api"
+  namespace: "core_graphics"
+  description: "Enable support for the Vulkan 1.4 instance API"
+  bug: "370568136"
+  is_fixed_read_only: true
+}