this PR adds support for the coder.envFrom value to the Helm chart. this will allow for Coder's environment variables to be passed from a single secret.

i'm pushing this in draft mode, because there is one caveat; the $hasAccessURL variable cannot identify if CODER_ACCESS_URL is set in the secret, so it will always default to the cluster-internal URL unless the access URL is specified using the traditional coder.env variable.

ideally, we parse the vars from the secret and pass them into the existing containers.env section in the template, but I have not gotten this to work. something akin to:

{{ if .Values.coder.envFrom }}
{{- range $secretKey, $secretValue := .Values.coder.envFrom }}
# Handle the coder.envFrom case
{{- range $key, $value := dict $secretValue }}
- name: {{ $key.name }}
  value: {{ $value | b64dec | quote }}
{{- end }}
{{- end }}
{{- end }}