Cut 1.18.16 release

[davidnuzik]

Upstream: kubernetes/sig-release#1465

Notice:
Upstream plans to get patch releases out by 2/17/2021.
v1.17 has reached end of life upstream. We follow what upstream does with releases, and v1.17 will not be included in this month's patch releases as there is nothing to release from upstream.

Summary:
Task covering patch release work.
Dev Complete: 2/12/2021

List of required releases:
To release as soon as able for QA:

• v1.18.16-rc1+k3s1

To release once have approval from QA:

• v1.18.16+k3s1

Prep work:

• PM: Dev and QA team to be notified of the incoming releases - send calendar invite
• PM: Dev and QA team to be notified of the date we will mark the latest release as stable - send calendar invite
• QA: Review changes and understand testing efforts
• Release Captain: Prepare release notes in our private release-notes repo (submit PR for changes taking care to carefully check links and the components, once merged, create the release in GitHub and mark as a draft and check the pre-release box, fill in title, set target release branch, leave tag version blank for now until we are ready to release)
• QA: Validate and close out all issues in the release milestone.

Vendor and release work:

• Release Captain: Vendor in the new patch version and release rancher/kubernetes
• Release Captain: Tag and release any necessary RCs for QA to test KDM
• Release Captain: Tag and release when have QA approval

Post-Release work:

• Release Captain: Once release is fully complete (CI is all green and all release artifacts exist), edit the release, uncheck "Pre-release", and save.
• PM: Close the milestone in GitHub.

[davidnuzik]

Closing; released.