Generate config for INTEROP tests on 4.18

[mgencur]

https://issues.redhat.com/browse/SRVCOM-3401

• Configuration for a candidate release of OpenShift now has to be specified explicitly. Previously, we generated them automatically by taking the highest version of OpenShift in config, bumping the minor version, and creating the config for the candidate release. Now, we need to be able to specify which custom configs will be run for each version of OpenShift - including this candidate version.
• Add tests for candidate OCP 4.18 explicitly for all repositories, but only for the latest version Serverless 1.36.
• Add INTEROP config for OpenShift 4.18. This is supposed to replace manual changes like in this PR: [INTEROP-7533] Expand OCP CI Serverless to OCP 4.18. openshift/release#57252 (it's error prone and requires multiple reviews from our team).
• Remove older interop tests for OCP <=4.17

When merging this PR, the following config will be generated: openshift/release#58680

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[mgencur]

@ReToCode Could you take a look? Thanks