Pass-through PROXY environment to Replicated SDK deployment

[divolgin]

What this PR does / why we need it:

When kotsadm is configured to use proxy at install time, Replicated SDK chart must also be configured with the same proxy settings.

Which issue(s) this PR fixes:

https://app.shortcut.com/replicated/story/111175/support-for-installing-behind-a-proxy

Does this PR require a test?

Unit tests updates. The change manually tested with a real proxy:

$ kubectl -n dmitriykots2 describe deployment replicated | grep Environment -A 10
    Environment:
      HTTP_PROXY:                    http://10.128.0.23:3128
      HTTPS_PROXY:                   http://10.128.0.23:3128
      NO_PROXY:                      10.96.0.1,35.225.92.50,kotsadm-rqlite,kotsadm-postgres,kotsadm-minio,kotsadm-api-node
      REPLICATED_NAMESPACE:           (v1:metadata.namespace)
      REPLICATED_POD_NAME:            (v1:metadata.name)
      DISABLE_OUTBOUND_CONNECTIONS:  false
      IS_HELM_MANAGED:               true
      HELM_RELEASE_NAME:             replicated
      HELM_RELEASE_NAMESPACE:        dmitriykots2
      HELM_PARENT_CHART_URL:         

Does this PR require a release note?

- When `--http-proxy`, `--https-proxy`, and `--no-proxy` flags are used with `kots install` command, the same values will be configured in the `replicated` deployment.

Does this PR require documentation?