decouple openshift-installer from release version

1. Proposed title of this feature request

decouple openshift-installer from release version

2. What is the nature and description of the request?

Create an openshift IPI installer that is always updated with the latest installation fixes, but is decoupled from the version of OCP that a user wants to install.

3. Why does the customer need this? (List the business requirements here)
 
I'm a PM for OpenShift Dedicated and ROSA. The openshift installation process has lots of bugs. In general, it's extremely painful for us to wait for the next OCP z-stream version or next minor release to get some installer fix. We're constantly having to build our own internal systems to compensate for the shortcomings of the OCP installer and for the delays in getting the fixes we need through the z-stream process. Even if next week's installer binary has fixes we need, that doesn't help our customers who refuse to install anything newer than current-y-minus-2 versions. It doesn't help our CI jobs testing N-2, N-3, etc.
 
What would help us is moving to a model where the installer is more of a decoupled service (i.e. not coupled to a specific release image) that we could consume to install any version of OCP. If we could do `openshift-installer-latest --version=ancient-4.8.25 my-cluster-1` where openshift-installer-latest has all the latest fixes, no matter what ancient version of OCP a ROSA user wants, that would solve our problem.
 
It would also alleviate our burden of building compensatory services to fill that gap – even if you fix the bugs in 4.11-latest this week, we need to build internal services to compensate for the bugs continuing to exist in 4.10, 4.9, 4.8, and 4.7. And we can't delete these compensatory services until we no longer allow installation of anything < fixed-version.
 
The best solution is one where installation is a decoupled "service" (could still be a binary) that constantly receives installer fixes immediately but still knows how to install any old version of OCP.

4. List any affected packages or components.

openshift-install

cc julim dhellman@redhat.com