[Impeller] Don't override user specification on Vulkan validation in unopt. (flutter#54816)

This overrides the documented behavior silently but only in unopt. Make opt and unopt modes behave the same. Disabling validation is frequently necessary to test behavior on simulators or when connecting to Renderdoc.

Author: chinmaygarde

impeller/renderer/backend/vulkan/context_vk.cc

@@ -157,18 +157,8 @@ void ContextVK::Setup(Settings settings) {
   auto& dispatcher = VULKAN_HPP_DEFAULT_DISPATCHER;
   dispatcher.init(settings.proc_address_callback);
 
-  // Enable Vulkan validation if either:
-  // 1. The user has explicitly enabled it.
-  // 2. We are in a combination of debug mode, and running on Android.
-  // (It's possible 2 is overly conservative and we can simplify this)
-  auto enable_validation = settings.enable_validation;
-
-#if defined(FML_OS_ANDROID) && !defined(NDEBUG)
-  enable_validation = true;
-#endif
-
   auto caps = std::shared_ptr<CapabilitiesVK>(new CapabilitiesVK(
-      enable_validation, settings.fatal_missing_validations));
+      settings.enable_validation, settings.fatal_missing_validations));
 
   if (!caps->IsValid()) {
     VALIDATION_LOG << "Could not determine device capabilities.";