Checkpoint RAM prefetch

[Gamekiller48]

Current situation:
In the settings you can select how many models to keep in RAM, to enable quick switching between them.
You can also automate image generation using X/Y plots.
The problem is that currently automatically switching between models/checkpoints is incredibly time consuming, because only the last few used models stay in RAM.

So the idea: when doing an X/Y Plot and one of the axis is "Checkpoint name" and number of models to keep in RAM is >1, prioritize loading the next checkpoint in the list into RAM as opposed to keeping the last models.

[fractal-fumbler]

check the lastest version of webui.
loading times of checkpoints get decsreased