fix(maxprocs): gracefully handle cgroup permission errors

[SAY-5]

What does this PR do?

Fixes #7653.

When KEDA pods run in an environment where the cgroup CPU files are not readable (for example, under a restricted SecurityContext that denies access to /sys/fs/cgroup/cpu.max, or on certain managed Kubernetes offerings that mount cgroups read-only), go.uber.org/automaxprocs's maxprocs.Set returns a permission error:

failed to set max procs
 {"error": "open /sys/fs/cgroup/cpu.max: permission denied"}

Today all three callers — cmd/operator/main.go, cmd/webhooks/main.go, and cmd/adapter/main.go — treat that error as fatal and call os.Exit(1). The result is a CrashLoopBackOff with no way to bring KEDA up at all, even though the only consequence of the failure is that GOMAXPROCS cannot be derived from cgroup quota. Go's runtime default (runtime.NumCPU()) is already a safe fallback.

Fix

pkg/util/maxprocs.go now:

1. Inspects the error returned by maxprocs.Set.
2. If it is an fs.ErrPermission, logs a warning via the same klog.Logger (so it is still visible in pod logs) and returns nil.
3. Otherwise propagates the error unchanged, preserving today's behavior for genuinely unexpected failures.

This lets KEDA start in locked-down environments while still surfacing the misconfiguration in logs. Non-permission errors (malformed cgroup data, I/O errors, etc.) remain fatal as before.

Which issue(s) this PR fixes

Fixes #7653

Checklist

• Commits are signed with Developer Certificate of Origin (DCO)
• A changelog entry was added under Unreleased → Fixes
• Change is trivial enough to not require unit tests (single call-site, behavior change is "convert permission error → warning")

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[rickbrouwer]

duplicate (#7655)