plugin scheduler: run iceberg and lifecycle lanes concurrently (#8821)

* plugin scheduler: run iceberg and lifecycle lanes concurrently

The default lane serialises job types under a single admin lock
because volume-management operations share global state. Iceberg
and lifecycle lanes have no such constraint, so run each of their
job types independently in separate goroutines.

* Fix concurrent lane scheduler status

* plugin scheduler: address review feedback

- Extract collectDueJobTypes helper to deduplicate policy loading
  between locked and concurrent iteration paths.
- Use atomic.Bool instead of sync.Mutex for hadJobs in the concurrent
  path.
- Set lane loop state to "busy" before launching concurrent goroutines
  so the lane is not reported as idle while work runs.
- Convert TestLaneRequiresLock to table-driven style.
- Add TestRunLaneSchedulerIterationLockBehavior to verify the scheduler
  acquires the admin lock only for lanes that require it.
- Fix flaky TestGetLaneSchedulerStatusShowsActiveConcurrentLaneWork by
  not starting background scheduler goroutines that race with the
  direct runJobTypeIteration call.

weed/admin/plugin/scheduler_status.go

@@ -195,6 +195,21 @@ func (r *Plugin) setSchedulerLoopState(jobType, phase string) {
 	r.schedulerLoopMu.Unlock()
 }
 
+// setSchedulerLoopStateForJobType keeps the aggregate scheduler state and the
+// owning lane state in sync while a specific job type is active.
+func (r *Plugin) setSchedulerLoopStateForJobType(jobType, phase string) {
+	if r == nil {
+		return
+	}
+	r.setSchedulerLoopState(jobType, phase)
+	if jobType == "" {
+		return
+	}
+	if ls := r.lanes[JobTypeLane(jobType)]; ls != nil {
+		r.setLaneLoopState(ls, jobType, phase)
+	}
+}
+
 func (r *Plugin) recordSchedulerIterationComplete(hadJobs bool) {
 	if r == nil {
 		return
@@ -251,7 +266,6 @@ func (r *Plugin) aggregateLaneLoopStates() schedulerLoopState {
 	return agg
 }
 
-
 // --- Per-lane loop state helpers ---
 
 func (r *Plugin) setLaneLoopState(ls *schedulerLaneState, jobType, phase string) {