Add new infeasible.rs crate

[Byte-Lab]

We want to avoid every scheduler implementation from having to implement
load balancing, but we also want to enable sufficient flexibility where
not every program has to have the same partition of scheduling domains,
etc. To enable this, a new load_balance crate is added which
encapsulates all of the logic for being given duty cycle and weight, and
performing the necessary math to adjust for infeasibility.

In addition, update scx_rusty to use the new crate.

[Byte-Lab]

The CI failure is an scx_qmap timeout:

EXIT: runnable task stall (kworker/2:1[53] failed to run for 6.016s)
[   18.812322] ACPI: PM: Preparing to enter system sleep state S5
[   18.813521] kvm: exiting hardware virtualization
[   18.813805] reboot: Power down
FAIL: scx_qmap

scx_qmap is another pure example scheduler, so I think we can similarly put it in the no-timeout bucket.

[arighi]

The CI failure is an scx_qmap timeout:

EXIT: runnable task stall (kworker/2:1[53] failed to run for 6.016s)
[   18.812322] ACPI: PM: Preparing to enter system sleep state S5
[   18.813521] kvm: exiting hardware virtualization
[   18.813805] reboot: Power down
FAIL: scx_qmap

scx_qmap is another pure example scheduler, so I think we can similarly put it in the no-timeout bucket.

I agree, and scx_userland as well. See #160 .

[Byte-Lab]

@htejun pushed a number of changes, please feel free to take another look. The comments that I haven't directly addressed are still left unresolved above, but everything else should have been addressed so let me know if you see otherwise.

[htejun]

I still find the name confusing given that all it does is solving infeasible weights (or is the plan to expand on it?) and it feels like leaving generic names like LoadCalc to actual scheduler implementations would be better, but this is definitely a nitpick. Please feel free to merge.

[Byte-Lab]

I still find the name confusing given that all it does is solving infeasible weights (or is the plan to expand on it?) and it feels like leaving generic names like LoadCalc to actual scheduler implementations would be better, but this is definitely a nitpick. Please feel free to merge.

Fair enough, I updated it to infeasible.rs. We can always further adjust it later if we need to.