Use the existing expandTo32bit mode in the texture decoder instead of
the backend-specific switches and stuff.
Just gets rid of a bunch of redundant code and makes further changes
easier.
When lazy loading, let's clear cached replacement data on disable.
This is purges memory immediately, and also allows force-reloading
textures by toggling the setting.
To be safe, gating this behind the related AllowLargeFBTextureOffsets,
which is also required for the effect to work.
Additionally, fixes the offset check for X offsets, which I guess is a
very small risk.
Could probably also be fixed by changing the heuristic a bit, but since
we're in heuristic land anyway and close to a release, I feel this is
the safest option.
Also sneaks in a logspam reduction
This is used by several games to render to the alpha channel of RGBA4444
images, which cannot normally be done directly on the PSP.
Can be used as a far more efficient replacement for
ReinterpretFramebuffers/ShaderColorBitmask
