Execute btp-manager tests on many k8s versions at once

[PK85]

Description

We are asked to test BTP-Manager on new k8s versions every month. We need to automate this process.

Info: right now SKRs run on k8s v1.26.

AC

• [x] 0) Check how to fetch k8s supported versions by k3s
• [x] 1) Reuse pipeline where we run k3s and create matrix tests (investigate GA feature about that)
• [x] 2) Check if we run those matrix tests only when releasing or on PRs too (on both)
• [x] 3) General test execution must not take longer than without matrix tests
• [x] 4) Release - default 3, overridden by input parameters, last defined by minor version (not patch)

Expected result

• We know that BTP Manager works on all new k8s versions.

Info

• https://docs.github.com/en/actions/using-jobs/using-a-matrix-for-your-jobs

[jaroslaw-pieszka]

Matrix can be created dynamically as an output from one of previous jobs.

[jaroslaw-pieszka]

E2E tests done in parallel for selected k8s/k3s versions #488 Selecting the most recent patch for n last minors #489