Layer Settings need a way to validate VkLayerSettingEXT

[spencer-lunarg]

Brought up in KhronosGroup/Vulkan-ValidationLayers#9028

I have no good way in the Validation Layers (without me, and every other layer having to hand-write it) to make sure the VkLayerSettingEXT passed in from the app

1. Is not using a pSettingName that doesn't exists (aka, a setting was removed and they are still setting it)
2. Validate the type is correct (you try setting INT32 of 1 or FLOAT32 of 1.0 instead of using a BOOL32

[spencer-lunarg]

Another issue I realized is in the JSON we just list things are INT for vkconfig, but have no way to know if that means the setting is actually VK_LAYER_SETTING_TYPE_INT32_EXT or VK_LAYER_SETTING_TYPE_UINT32_EXT