Update loki push path

[joe-elliott]

What this PR does / why we need it:
All of the other Loki paths were updated to be versioned and contain a /loki prefix. This finishes the job by also updating the push path.

Special notes for your reviewer:

• Anything under /docs was ignored due to @rfratto 's pending documentation PR. I double checked he covered the path change.
• This makes several changes to production configs and should be checked carefully
  • promtail helm chart and version were updated
  • fluentd plugin was updated. does the gem version need to be incremented?
  • loki gateway was updated to support both old and new paths
• Should some of these updates wait for when we have these new paths active in the prod environments?

Checklist

• Documentation added
• Tests updated

[cyriltovena]

fluentd plugin was updated. does the gem version need to be incremented?

Yes let's create an issue, is it the case for the docker driver too ? I think so.

[rfratto]

Cool, this LGTM but I'd like a second person to approve it.
@cyriltovena I think the docker driver gets published by CI every time we do a tag.

[cyriltovena]

LGTM

[joe-elliott]

• Updated gem version due to path change
• Reverted helm chart changes and helm chart version
• Docker driver does not need a version update. It builds directly off of the tip of master and is probably verisoned when we do a loki release along with promtail and loki.