scheduler: RescheduleTracker dropped if follow-up fails placements (#12319)

When an allocation fails it triggers an evaluation. The evaluation is processed
and the scheduler sees it needs to reschedule, which triggers a follow-up
eval. The follow-up eval creates a plan to `(stop 1) (place 1)`. The replacement
alloc has a `RescheduleTracker` (or gets its `RescheduleTracker` updated).

But in the case where the follow-up eval can't place all allocs (there aren't
enough resources), it can create a partial plan to `(stop 1) (place 0)`. It then
creates a blocked eval. The plan applier stops the failed alloc. Then when the
blocked eval is processed, the job is missing an allocation, so the scheduler
creates a new allocation. This allocation is _not_ a replacement from the
perspective of the scheduler, so it's not handed off a `RescheduleTracker`.

This changeset fixes this by annotating the reschedule tracker whenever the
scheduler can't place a replacement allocation. We check this annotation for
allocations that have the `stop` desired status when filtering out allocations
to pass to the reschedule tracker. I've also included tests that cover this case
and expands coverage of the relevant area of the code.

Fixes: https://github.com/hashicorp/nomad/issues/12147
Fixes: https://github.com/hashicorp/nomad/issues/17072

api/allocations.go

@@ -558,7 +558,8 @@ type GenericResponse struct {
 
 // RescheduleTracker encapsulates previous reschedule events
 type RescheduleTracker struct {
-	Events []*RescheduleEvent
+	Events         []*RescheduleEvent
+	LastReschedule string
 }
 
 // RescheduleEvent is used to keep track of previous attempts at rescheduling an allocation