Don't count unscaled frequently changing texels.

May cause more things to be scaled per frame (especially if first textures
on a frame are frequently changing.)
Forgive freq. changed tex if they mend their ways.
Qt: Split GPU from Core to fix Debugger conflict.
Reduce change frequency limit for texscaling.

Since we have the texels limit now, this should allow more textures to be
scaled safely.  Also, it may detect alpha optimizations in more textures,
since we currently skip them for frequently changed textures.
Validate stride when using clut, more reporting.
Centralize render-to-tex logic, support mirrors.

Now everything is decided in AttachFramebuffer().
Report decoding a texture from a VRAM mirror.

Might mainly be depth textures?
Log more info about skipped subarea renders.
Skip memcpy fb download when already downloaded.

Fixes Final Fantasy Tactics lag, discussion in #6308.
Merge pull request #6320 from unknownbrackets/texcache

Validate render to texture better, report more, and support vram mirrors
Merge pull request #6321 from unknownbrackets/texscaling

Reduce some texture scaling limits to rely on texels instead
Consistently mark vfb dirty after drawing to it.
Support inter-buffer memcpy transfer.

Seeing some games using it like 3rd Birthday uses block transfers, to copy
a frame to the other buffer.
Merge pull request #6322 from unknownbrackets/gpu-blocktransfer

Support inter-buffer memcpy, mark vfb dirty when blitting to it, etc.
Correct timing on resume, avoids small speed burst when resuming gameplay from pause
wasPaused int->bool
Allow only a small number of "InvalidateAll" operations per frame on the texture cache.

Reduces stutter in FF:Type0 tutorial end scene a bit more.
Support drag-and-drop of savestate files.

Most likely you want to load the state, not see an error message.
Support render-to-offset within a framebuffer.

Fixes #6324.
Merge pull request #6325 from unknownbrackets/ui-tweaks

Support drag-and-drop of savestate files