Support for deployment/install/update of CRW on OCP 3.11 & 4.8-4.9 ends with 2.15.z

The DevWorkspace Operator 0.9+ requires OpenShift 4.8+ features in its design, which means that it is not installable in an OpenShift 3.11 EUS or 4.6 EUS cluster.

In order to maintain CRW support on OCP 3.11 and 4.6, it's necessary to ensure it's still possible to install/update/deploy CRW on 3.11 and 4.6 once DevWorkspaces support is enabled by default.

Devfile v2.0 features will generally be incompatible with OCP 3.11 and 4.6, as the DevWorkspace Operator is required for handling the underlying DevWorkspace object.

However, since 4.8 has been deemed an EUS release, we won't be supporting OCP 4.6 as of CRW 2.13+.

Support Timelines - see https://cloud.redhat.com/blog/time-is-on-your-side-a-change-to-the-openshift-4-lifecycle:

• OCP 3.11 EUS EOL: June 21 2022
• OCP 4.6 EUS EOL: Oct 2022
• OCP 4.8 EUS EOL: Feb 2023
• OCP 4.10 EUS EOL: Sep 2023

So the plan here is to have 2.15.z releases (if needed) after 2.16.0 is live, which will support existing CRW customers on OCP 3.11.

After June 2022, OCP 3.11 support will end. But support for CRW 2.x in OCP 3.11 will end when CRW 2.16.0 occurs (in April 2022).

DONE:

• update Comet entries so that Freshmaker will ONLY update latest containers (single-stream)
• maintain old "latest" channel for 2.15, while new "stable" channel is used for 2.16+; NOTE that once 2.16 is out, 2.15.z updates end

TODOs:

• update 2.15 release notes to state that 2.15 is the last release that will support OCP 3.11 and OCP 4.8-4.9
• release 2.16; ensure 2.16 release notes / support matrix states support in CRW 2.16 is for OCP 4.10