… of rolling back all work (armadaproject#4559)

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#### What type of PR is this?

Enhancement

#### What this PR does / why we need it

Previously, when the scheduler hit its timeout during the scheduling
cycle, it would return an error and discard all work, even jobs that
were successfully scheduled before the timeout.

This change implements a two-tier timeout system for the scheduler to
handle long scheduling cycles gracefully.

This change introduces a new config field in the scheduler:
`newJobsSchedulingTimeout`:
```
  # scheduler.config.yaml
  scheduling:
    # Hard timeout - absolute maximum duration for a scheduling cycle.
    # When exceeded, cycle aborts with error and discards all work.
    maxSchedulingDuration: 10s

    # Soft timeout - stop scheduling new jobs after this duration.
    # Evicted jobs continue to be rescheduled until hard timeout.
    # Set to 0 to disable soft timeout behavior.
    # Must be less than maxSchedulingDuration when non-zero.
    newJobsSchedulingTimeout: 8s
```

#### Expected output

When soft timeout fires:
```
  INFO Soft timeout reached for pool default, switching to evicted-only mode
  INFO Looping through candidate gangs for pool default...
  INFO Scheduled 873 jobs for pool default
```

When hard timeout fires (unchanged behavior):
```
  ERROR hard timeout: context deadline exceeded
```

#### How to test

Check the section at the end called **Additional Files** for the test
script and test Armada job.

1. Configure scheduler with a short timeout in
`_local/scheduler/config.yaml`:
```
maxSchedulingDuration: 200ms
```
2. Configure fake executor with enough capacity in
`_local/fakeexecutor/config.yaml`:
```
nodes:
  - name: "fake-node"
    count: 50
    allocatable:
      cpu: "64"
      memory: "256Gi"
```
3. Start the local environment: `goreman -f
_local/procfiles/fake-executor.Procfile start`
4. Create two test queues:
```
armadactl create queue queue-a
armadactl create queue queue-b
```
5. Run the following commands to generate jobs:
```
./scripts/submit-jobs.sh -c 5000 -q queue-a -j jobset-timeout-a example/fair-share-test.yaml
./scripts/submit-jobs.sh -c 5000 -q queue-b -j jobset-timeout-b example/fair-share-test.yaml
```
6. Assert that the following logs appear in the output of the scheduler:
```
  INFO Timeout reached for pool default, switching to evicted-only mode
  INFO Scheduling cycle interrupted by context deadline exceeded: scheduled 873 jobs for pool default
  INFO Scheduled on executor pool default in 19.983083ms with error <nil>
```

##### Additional Files
```
# scripts/submit-jobs.sh

#!/bin/bash
set -e

COUNT=1
JOBSET="test-jobset"
QUEUE="test-queue"
JOB_TEMPLATE=""
MAX_PARALLEL=50

while [[ $# -gt 0 ]]; do
    case $1 in
        -c|--count) COUNT="$2"; shift 2 ;;
        -j|--jobset) JOBSET="$2"; shift 2 ;;
        -q|--queue) QUEUE="$2"; shift 2 ;;
        -p|--parallel) MAX_PARALLEL="$2"; shift 2 ;;
        -*) echo "Unknown option $1"; exit 1 ;;
        *) JOB_TEMPLATE="$1"; shift ;;
    esac
done

[[ -z "$JOB_TEMPLATE" ]] && JOB_TEMPLATE="example/fair-share-test.yaml"
[[ ! -f "$JOB_TEMPLATE" ]] && echo "Error: $JOB_TEMPLATE not found" && exit 1

ARMADACTL="./armadactl"
[[ ! -f "$ARMADACTL" ]] && ARMADACTL="armadactl"

TEMP_DIR=$(mktemp -d)
trap "rm -rf $TEMP_DIR" EXIT

JOB_FILE="$TEMP_DIR/job.yaml"
sed -e "s/^jobSetId:.*/jobSetId: $JOBSET/" -e "s/^queue:.*/queue: $QUEUE/" "$JOB_TEMPLATE" > "$JOB_FILE"

$ARMADACTL create queue "$QUEUE" 2>/dev/null || true

echo "Submitting $COUNT batches to queue '$QUEUE' jobset '$JOBSET'..."

PIDS=()
for ((i=1; i<=COUNT; i++)); do
    $ARMADACTL submit "$JOB_FILE" >/dev/null 2>&1 &
    PIDS+=($!)
    if ((${#PIDS[@]} >= MAX_PARALLEL)) || ((i == COUNT)); then
        for pid in "${PIDS[@]}"; do wait $pid; done
        PIDS=()
        echo "Progress: $i/$COUNT"
    fi
done

echo "Done. Submitted $COUNT batches to queue '$QUEUE'"
```

```
# example/fair-share-test.yaml

queue: test-queue
jobSetId: fair-share-test
jobs:
  - namespace: default
    priority: 1000
    podSpec: &podspec
      terminationGracePeriodSeconds: 0
      restartPolicy: Never
      containers:
        - name: worker
          image: busybox:latest
          command: ["sleep", "3600"]
          resources:
            limits:
              memory: 64Mi
              cpu: 50m
            requests:
              memory: 64Mi
              cpu: 50m
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
  - namespace: default
    priority: 1000
    podSpec: *podspec
```

Signed-off-by: Dejan Zele Pejchev <pejcev.dejan@gmail.com>