scheduler: add reconciler annotations to completed evals

[tgross]

The output of the reconciler stage of scheduling is only visible via debug-level logs, typically accessible only to the cluster admin. We can give job authors better ability to understand what's happening to their jobs if we expose this information to them in the eval status command.

Add the reconciler's desired updates to the evaluation struct so it can be exposed in the API. This increases the size of evals by roughly 15% in the state store, or a bit more when there are preemptions (but we expect this will be a small minority of evals).

Ref: https://hashicorp.atlassian.net/browse/NMD-818
Fixes: #15564

Contributor Checklist

• Changelog Entry If this PR changes user-facing behavior, please generate and add a
  changelog entry using the make cl command.
• Testing Please add tests to cover any new functionality or to demonstrate bug fixes and
  ensure regressions will be caught.
• Documentation If the change impacts user-facing functionality such as the CLI, API, UI,
  and job configuration, please update the Nomad website documentation to reflect this. Refer to
  the website README for docs guidelines. Please also consider whether the
  change requires notes within the upgrade guide.
  • more comprehensive eval status and alloc status docs changes coming under separate PR

Reviewer Checklist

• Backport Labels Please add the correct backport labels as described by the internal
  backporting document.
• Commit Type Ensure the correct merge method is selected which should be "squash and merge"
  in the majority of situations. The main exceptions are long-lived feature branches or merges where
  history should be preserved.
• Enterprise PRs If this is an enterprise only PR, please add any required changelog entry
  within the public repository.

[tgross]

Example output of the updated eval status command with preemptions:

$ nomad eval status 4d832430
ID                 = 4d832430
Create Time        = 34s ago
Modify Time        = 34s ago
Status             = complete
Status Description = complete
Type               = service
TriggeredBy        = job-register
Job ID             = example2
Namespace          = default
Priority           = 100
Placement Failures = false
Previous Eval      = <none>
Next Eval          = <none>
Blocked Eval       = <none>

Reconciler Annotations
Task Group  Ignore  Place  Stop  Migrate  InPlace  Destructive  Canary  Preemptions
group       0       1      0     0        0        0            0       1

Preempted Allocations
ID        Job ID    Node ID   Task Group  Version  Desired  Status   Created   Modified
116e9046  example1  fb4cacda  group       0        run      running  1m9s ago  59s ago

Placed Allocations
ID        Node ID   Task Group  Version  Desired  Status   Created  Modified
a61edb08  fb4cacda  group       0        run      running  34s ago  18s ago

[jrasell]

LGTM!