Define a new "dynamic" upgrade scenario in CI framework

Follow up of CI session done in Sylva dev workshop

Background As the number of release branches increase we need to define more and more upgrade scenario, maintaining them in release branches become complex. It also lead to some error when we use them in the MR templates if they are not defined in the release branches.

Proposal This issue tracks a proposal from @mederic.deverdilhac to enhance our CI framework with the ability to have dynamic upgrade scenario.

Today we have:

.scenario_sylva-upgrade-from-1.4.x: # from 1.4.x to current
  extends:
    - .rolling-upgrade-timeout
  variables:
    DESCRIPTION: |
      Deploy the management cluster and perform a Sylva upgrade from the latest 1.4.x version to main.
    MGMT_INITIAL_REVISION: release-1.4
    MGMT_UPDATE_REVISION: "" # Use current commit
    WC_INITIAL_REVISION: release-1.4
    WC_UPDATE_REVISION: "" # Use current commit

We would like to have a detection of the following patterns:

• upgrade-from-
• upgrade-from--to

that would automatically determine the revision to use based on the name of the scenario

We need to keep the ability to manually define upgrade scenario (first check if exist otherwise try to parse)

it will also imply to change the ALLOWED_SCENARIO security to have something more dynamic

I would suggets to drop the "sylva" prefix that doesn't have any value