Support terminationGracePeriodSeconds for kas

What does this MR do?

As identified in gitlab-org/cluster-integration/gitlab-agent#279 (comment 1135424453), we don't have terminationGracePeriodSeconds for kas and this quite probably leads to dropped connections. Add support for setting this parameter so that we can tweak it in production. It normally defaults to 30 seconds, but here we bump it to 5 minutes by default to always give kas a bit more time to wrap up. This is important for self-managed customers.

Related issues

Relates to gitlab-org/cluster-integration/gitlab-agent#279 (closed).

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.