renovate: annotate KIND_VERSION and KUBECTL_VERSION in devcontainer

[vdaviot]

Summary

Annotates KIND_VERSION and KUBECTL_VERSION in .devcontainer/Dockerfile so they're picked up by the new shared platform-renovate preset's customManagers:dockerfileVersions. Tracks one of the four follow-ups listed in scality/platform-renovate#3 (the in-flight PR comment).

Why

scality/crl-operator#15 already adds annotations for OPERATOR_SDK_VERSION and GOLANGCI_VERSION in the same Dockerfile, but KIND_VERSION and KUBECTL_VERSION were left un-annotated. With the new shared preset (replaces the hand-rolled regex with customManagers:dockerfileVersions), this is the small follow-up that makes those two pins visible to Renovate.

Annotation choices

• KIND_VERSION: tracks kubernetes-sigs/kind GitHub releases. extractVersion=^v(?<version>.*)$ strips the leading v so the variable keeps its existing un-prefixed form (the v is added back at curl-time in the RUN line).
• KUBECTL_VERSION: tracks kubernetes/kubernetes GitHub releases (kubectl is part of the main k8s release). Same extractVersion for the same reason. This depName is in the new shared preset's operator-tooling group, so updates will be labelled deps/operator-tooling and grouped with kustomize/controller-tools/operator-sdk.

Merge order

This PR depends on the cascade of:

1. scality/platform-renovate#3 — the new shared preset
2. scality/crl-operator#15 — the per-repo extends collapse + the existing OPERATOR_SDK/GOLANGCI annotations

Best to merge in that order. The annotations themselves are inert until both prerequisites land (the # renovate: comments are simply ignored by Renovate without the matching custom manager active).

Test plan

• Run git rebase main after the prerequisites land — should auto-merge cleanly (the new annotation lines don't overlap with the OPERATOR_SDK/GOLANGCI annotation lines).
• On the next Renovate run, observe kind and kubectl appearing under the operator-tooling group on the Dependency Dashboard.