[helm] Mimic loki service account with canary account (grafana#7236)

**What this PR does / why we need it**:

Bring the Loki Canary service account in line with the Loki service
account, removing the post install hook, and sharing the top level
properties for `automountServiceAccountToken` and `imagePullSecrets`.
I'm open to creating canary specific values for these setting if needed,
but want to start by sharing the top level values to reduce config if
possible.

Also default canary to Appversion to be in sync with default Loki
version

**Which issue(s) this PR fixes**:
Fixes two issues raised in comments from @towolf (thanks!) on this
[PR](grafana#7173 (comment)).

Fixes grafana#7237

production/helm/loki/templates/loki-canary/_helpers.tpl

@@ -25,7 +25,7 @@ app.kubernetes.io/component: canary
 Docker image name for loki-canary
 */}}
 {{- define "loki-canary.image" -}}
-{{- $dict := dict "service" .Values.monitoring.selfMonitoring.lokiCanary.image "global" .Values.global.image "defaultVersion" "latest" -}}
+{{- $dict := dict "service" .Values.monitoring.selfMonitoring.lokiCanary.image "global" .Values.global.image "defaultVersion" .Chart.AppVersion -}}
 {{- include "loki.baseImage" $dict -}}
 {{- end -}}
 

production/helm/loki/templates/loki-canary/serviceaccount.yaml

@@ -7,8 +7,12 @@ metadata:
   labels:
     {{- include "loki-canary.labels" . | nindent 4 }}
   annotations:
-    "helm.sh/hook": post-install
   {{- with .Values.monitoring.selfMonitoring.lokiCanary.annotations }}
     {{- toYaml . | nindent 4 }}
   {{- end }}
+automountServiceAccountToken: {{ .Values.serviceAccount.automountServiceAccountToken }}
+{{- with .Values.serviceAccount.imagePullSecrets }}
+imagePullSecrets:
+  {{- toYaml . | nindent 2 }}
+{{- end }}
 {{- end }}