Previously, we would show the render-to-texture with its original
dimensions. While useful, this skewed the preview coordinates and was
sometimes confusing. Additionally, depth texturing didn't preview.
This pads and subsets the texture preview so it's the right size.
Followup to #16188 .
Further fixes the lens flare.
It confused me before that there are two sections of the track on
Sunset Drive where the sun is visible, but only on the second is the
lens flare sprite actually shown, which is rather weird.
Verified that exactly the same thing happens on hardware, so it's not a
an emulation problem! Rather seems like a glitch in the game itself.
With this wrong, we ended up drawing pixels that came from a DONT_CARE
init of the depal temp buffer, which was a pile of garbage on Android
and blank on PC.
Now, we seem to end up not drawing anything because the depal operation
results in transparent black into whatever is actually intended, but at
least the screen isn't full of glitches when the sun is visible on Adreno.
See issue #16083
