apply scripts: fail quickly on any sylva-units error

The sylvactl binary has restricted conditions in which it will exit early ; we can't extend this list too much because it would apply to all Kustomization and HelmReleases, and would result in stopping sylvactl even in the case where the error is due to a temporary intermediate step.

However, for the sylvactl watch call done right when using apply.sh to reconcile the sylva-units HelmRelease itself, we know that we shouldn't have temporary errors, and we will benefit from having quicker failure.

Example environment values:

_internal:
  test: '{{ include "does-not-exist" . }}'

Doing this results in:

status:
  conditions:
...
  - lastTransitionTime: "2024-07-04T13:12:18Z"
    message: 'Helm upgrade failed for release sylva-system/sylva-units with chart
      sylva-units@0.0.0-git+7b4c837f39fe.1: template: sylva-units/templates/units.yaml:6:31:
      executing "sylva-units/templates/units.yaml" at <include "interpret-values-gotpl"
      .>: error calling include: template: sylva-units/templates/_interpret-values.tpl:107:89:
      executing "interpret-values-gotpl" at <include "interpret-inner-gotpl">: error
      calling include: template: sylva-units/templates/_interpret-values.tpl:308:60:
      executing "interpret-inner-gotpl" at <include "interpret-inner-gotpl">: error
      calling include: template: sylva-units/templates/_interpret-values.tpl:277:28:
      executing "interpret-inner-gotpl" at <tpl $data $envAll>: error calling tpl:
      error during tpl function execution for "{{ include \"does-not-exist\" . }}":
      template: sylva-units/templates/units.yaml:1:3: executing "sylva-units/templates/units.yaml"
      at <include "does-not-exist" .>: error calling include: template: no template
      "does-not-exist" associated with template "gotpl"'
    observedGeneration: 11
    reason: UpgradeFailed
    status: "False"
    type: Ready

With the change done in this MR, apply.sh will exit instantly with:

🎯 Trigger reconciliation of units
trigger reconciliation of sylva-units HelmRelease...
  using forced reconciliation
  helmrelease.helm.toolkit.fluxcd.io/sylva-units annotated
 ✓ GitRepository/sylva-core - Resource is ready
 ✓ GitRepository/sylva-core - Resource is ready
 ✓ HelmChart/sylva-system-sylva-units - Resource is ready
 ✗ Exit condition matched for unit HelmRelease/sylva-units with reason: UpgradeFailed

Following resources were not ready when exit condition matched:
    * HelmRelease/sylva-units: UpgradeFailed - Helm upgrade failed for release sylva-system/sylva-units with chart sylva-units@0.0.0-git+1d79dafb69c7.1: template: sylva-units/templates/units.yaml:6:31: executing "sylva-units/templates/units.yaml" at <include "interpret-values-gotpl" .>: error calling include: template: sylva-units/templates/_interpret-values.tpl:107:89: executing "interpret-values-gotpl" at <include "interpret-inner-gotpl">: error calling include: template: sylva-units/templates/_interpret-values.tpl:308:60: executing "interpret-inner-gotpl" at <include "interpret-inner-gotpl">: error calling include: template: sylva-units/templates/_interpret-values.tpl:277:28: executing "interpret-inner-gotpl" at <tpl $data $envAll>: error calling tpl: error during tpl function execution for "{{ include \"does-not-exist\" . }}": template: sylva-units/templates/units.yaml:1:3: executing "sylva-units/templates/units.yaml" at <include "does-not-exist" .>: error calling include: template: no template "does-not-exist" associated with template "gotpl"