Also makes y_scale a dynamic parameter for EFB copies, as it doesn't
make sense to keep it as part of the uid, otherwise we're generating
redundant shaders.
Tested on a linux Intel Skylake integrated graphics with
blend_func_extended force-disabled, as it's the only platform I have
that doesn't crash with ubershaders and supports fb_fetch
This is a remake of https://github.com/dolphin-emu/dolphin/pull/3749
Full credit goes to phire.
Old message:
"If none of the texture registers have changed and TMEM hasn't been invalidated or changed in other ways, we can blindly reuse the old texture cache entries without rehashing.
Not only does this fix the bloom effect in Spyro: A Hero's Tail (The game abused texture cache) but it will also provide speedups for other games which use the same texture over multiple draw calls, especially when safe texture cache is in use."
Changed the pr per phire's instructions to only return the current texture(s) if none of the texture registers were changed. If any texture register was changed, fall back to the default hashing and rebuilding textures from memory.
