Enable CONFIG_PSI in the default kernel

[K900]

Is your feature request related to a problem? Please describe.
The current default WSL kernel is built with CONFIG_PSI unset, which means the process stall information metrics are not collected or exposed, so things that rely on those (notably systemd-oomd, a userspace early-OOM service) do not work.

Describe the solution you'd like
CONFIG_PSI=y is enabled in the kernel.

Describe alternatives you've considered
Leave things as they are.

Additional context
While systemd-oomd may seem unhelpful, as the VM's memory is already limited, it does help prevent the VM itself from locking up when under heavy memory pressure, forcing the user to kill the entire VM and possibly lose data.

[soredake]

@kelsey-steele Hi! I've seen that you've fixed #8302, can you look at this issue too, please?

[wrightleft]

This would really help with compiling in WSL2 where I keep running out of memory and the whole WSL2 system comes to a halt.