[embedder] Ensure destruction called on present

[cbracken]

This is a followup to #38038.

In that patch, a destruction callback for textures created via the FlutterRendererConfig callbacks (as opposed to by the FlutterCompositor callbacks) was added and passed through to the texture info attached to the SurfaceFrame generated in GPUSurfaceMetalSkia::AcquireFrameFromMTLTexture (called via GPUSurfaceMetalSkia::GetMTLTexture, which invokes the get_next_drawable_callback), however, in order for the destruction callback to make it to the presented Skia texture, it needs to be passed through to the present callback here:
https://github.com/flutter/engine/blob/5545ccf8719c9568d8f521f9f18a869ca9e10056/shell/gpu/gpu_surface_metal_skia.mm#LL233
which is invoked by the submit callback passed to Skia:
https://github.com/flutter/engine/blob/5545ccf8719c9568d8f521f9f18a869ca9e10056/shell/gpu/gpu_surface_metal_skia.mm#LL239

The present callback is implemented in EmbedderSurface::PresentTexture, which invokes the present callback registered in FlutterMetalRendererConfig.present_drawable_callback. This patch ensures that the destruction callback is passed through to Skia's present callback so destruction occurs in the right place.

Issue: flutter/flutter#116381

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[flutter-dashboard]

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[cbracken]

Found a way to update the test to ensure the timing of destruction: ensure it doesn't happen until after we get the surface present callback.