render/vulkan: wait for idle queue before destroying render buffer

This fixes the following validation errors when shutting down Sway:

    00:00:01.263 [wlr] [render/vulkan/vulkan.c:65] Validation Error: [ VUID-vkDestroyFramebuffer-framebuffer-00892 ] Object 0: handle = 0x62e00003c400, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xdb308312 | Cannot call vkDestroyFramebuffer on VkFramebuffer 0x2e2cd000000002b[] that is currently in use by a command buffer. The Vulkan spec states: All submitted commands that refer to framebuffer must have completed execution (https://www.khronos.org/registry/vulkan/specs/1.3-extensions/html/vkspec.html#VUID-vkDestroyFramebuffer-framebuffer-00892) (VUID-vkDestroyFramebuffer-framebuffer-00892)
    00:00:01.264 [wlr] [render/vulkan/vulkan.c:65] Validation Error: [ VUID-vkDestroyImage-image-01000 ] Object 0: handle = 0x62e00003c400, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0xf2d29b5a | Cannot call vkDestroyImage on VkImage 0x3fbcd60000000028[] that is currently in use by a command buffer. The Vulkan spec states: All submitted commands that refer to image, either directly or via a VkImageView, must have completed execution (https://www.khronos.org/registry/vulkan/specs/1.3-extensions/html/vkspec.html#VUID-vkDestroyImage-image-01000) (VUID-vkDestroyImage-image-01000)

render/vulkan/renderer.c

@@ -569,6 +569,13 @@ static void destroy_render_buffer(struct wlr_vk_render_buffer *buffer) {
 
 	VkDevice dev = buffer->renderer->dev->dev;
 
+	// TODO: asynchronously wait for the command buffers using this render
+	// buffer to complete (just like we do for textures)
+	VkResult res = vkQueueWaitIdle(buffer->renderer->dev->queue);
+	if (res != VK_SUCCESS) {
+		wlr_vk_error("vkQueueWaitIdle", res);
+	}
+
 	vkDestroyFramebuffer(dev, buffer->framebuffer, NULL);
 	vkDestroyImageView(dev, buffer->image_view, NULL);
 	vkDestroyImage(dev, buffer->image, NULL);