Add aws_auth.token_secs_remaining to gundeck, cargohold, galley

[smatting]

This PR is a follow-up to #2473 . It adds the metric aws_auth.token_secs_remaining to:

• gundeck
• cargohold
• galley

brig already contains the metric.

This PR removes the metric aws_auth.token_is_reference from brig (exists only there)

Checklist

• The PR Title explains the impact of the change.
• The PR description provides context as to why the change should occur and what the code contributes to that effect. This could also be a link to a JIRA ticket or a Github issue, if there is one.
• changelog.d contains the following bits of information (details):
  • A file with the changelog entry in one or more suitable sub-sections. The sub-sections are marked by directories inside changelog.d.

[flokli]

What about cannon, proxy and spar?

[akshaymankar]

What about cannon, proxy and spar?

They don't talk to AWS

[flokli]

They don't talk to AWS

Great!