stop pointing to ci-deployment-values main, reference a tag instead

This MR introduces a CI config change to stop having sylva-core main point to ci-deployment-values main, and point to a tag of ci-deployment-values instead.

Today we often have a painful chicken-n-egg issue with a sylva-core MR that needs a ci-deployment-values evolution, but the ci-deployment-values MRs can't merge before the sylva-core MRs does (or else other CI runs from main would fail) -- a typical case is a sylva-core MR that adds a new optional unit that we want to test in a capo-misc or capm3-misc job.

But we have other cases as well, e.g the "keycloak in base deps" evolution !2183 (merged) and sylva-projects/sylva-elements/ci-tooling/ci-deployment-values!43 (merged).

One detail: with #1550 (closed) in mind, I'm introducing the CI_VALUES_REVISION which will in the context of #1550 (closed) fully replace (MANAGEMENT|WC)_(INITIAL|UPDATE)_CI_VALUES_REVISION, I think.