scx_layered: Fix verifier errors

[hodgesds]

Fix verifier errors when using different DSQ iteration algorithms and cleanup some code.

weight:

$ sudo ./target/release/scx_layered  f:/home/hodgesd/user.json --dsq-iter-algo  weight 
21:38:05 [INFO] CPUs: online/possible=176/176 nr_cores=88
21:38:05 [INFO] libbpf: struct_ops layered: member cgroup_init not found in kernel, skipping it as it's set to zero

21:38:05 [INFO] libbpf: struct_ops layered: member cgroup_exit not found in kernel, skipping it as it's set to zero

21:38:05 [INFO] libbpf: struct_ops layered: member cgroup_prep_move not found in kernel, skipping it as it's set to zero

21:38:05 [INFO] libbpf: struct_ops layered: member cgroup_move not found in kernel, skipping it as it's set to zero

21:38:05 [INFO] libbpf: struct_ops layered: member cgroup_cancel_move not found in kernel, skipping it as it's set to zero

21:38:05 [INFO] libbpf: struct_ops layered: member cgroup_set_weight not found in kernel, skipping it as it's set to zero

21:38:05 [INFO] Layered Scheduler Attached. Run `scx_layered --monitor` for metrics.
^CEXIT: Scheduler unregistered from user space

linear:

$ sudo ./target/release/scx_layered  f:/home/hodgesd/user.json --dsq-iter-algo  linear 
21:38:36 [INFO] CPUs: online/possible=176/176 nr_cores=88
21:38:36 [INFO] libbpf: struct_ops layered: member cgroup_init not found in kernel, skipping it as it's set to zero

21:38:36 [INFO] libbpf: struct_ops layered: member cgroup_exit not found in kernel, skipping it as it's set to zero

21:38:36 [INFO] libbpf: struct_ops layered: member cgroup_prep_move not found in kernel, skipping it as it's set to zero

21:38:36 [INFO] libbpf: struct_ops layered: member cgroup_move not found in kernel, skipping it as it's set to zero

21:38:36 [INFO] libbpf: struct_ops layered: member cgroup_cancel_move not found in kernel, skipping it as it's set to zero

21:38:36 [INFO] libbpf: struct_ops layered: member cgroup_set_weight not found in kernel, skipping it as it's set to zero

21:38:36 [INFO] Layered Scheduler Attached. Run `scx_layered --monitor` for metrics.
^CEXIT: Scheduler unregistered from user space

round_robin:

]$ sudo ./target/release/scx_layered  f:/home/hodgesd/user.json --dsq-iter-algo  round_robin
21:39:07 [INFO] CPUs: online/possible=176/176 nr_cores=88
21:39:07 [INFO] libbpf: struct_ops layered: member cgroup_init not found in kernel, skipping it as it's set to zero

21:39:07 [INFO] libbpf: struct_ops layered: member cgroup_exit not found in kernel, skipping it as it's set to zero

21:39:07 [INFO] libbpf: struct_ops layered: member cgroup_prep_move not found in kernel, skipping it as it's set to zero

21:39:07 [INFO] libbpf: struct_ops layered: member cgroup_move not found in kernel, skipping it as it's set to zero

21:39:07 [INFO] libbpf: struct_ops layered: member cgroup_cancel_move not found in kernel, skipping it as it's set to zero

21:39:07 [INFO] libbpf: struct_ops layered: member cgroup_set_weight not found in kernel, skipping it as it's set to zero

21:39:07 [INFO] Layered Scheduler Attached. Run `scx_layered --monitor` for metrics.
^CEXIT: Scheduler unregistered from user space

weight no topo:

$ sudo ./target/release/scx_layered  f:/home/hodgesd/user.json --dsq-iter-algo  weight -t
21:39:36 [INFO] Disabling topology awareness
21:39:36 [INFO] CPUs: online/possible=176/176 nr_cores=88
21:39:36 [INFO] libbpf: struct_ops layered: member cgroup_init not found in kernel, skipping it as it's set to zero

21:39:36 [INFO] libbpf: struct_ops layered: member cgroup_exit not found in kernel, skipping it as it's set to zero

21:39:36 [INFO] libbpf: struct_ops layered: member cgroup_prep_move not found in kernel, skipping it as it's set to zero

21:39:36 [INFO] libbpf: struct_ops layered: member cgroup_move not found in kernel, skipping it as it's set to zero

21:39:36 [INFO] libbpf: struct_ops layered: member cgroup_cancel_move not found in kernel, skipping it as it's set to zero

21:39:36 [INFO] libbpf: struct_ops layered: member cgroup_set_weight not found in kernel, skipping it as it's set to zero

21:39:36 [INFO] Layered Scheduler Attached. Run `scx_layered --monitor` for metrics.
^CEXIT: Scheduler unregistered from user space