CLOUDP-295785 - copy kubectl-mongodb plugin to ./bin/kubectl-mongodb for code snippets tests

[MaciejKaras]

Summary

We need to make kubectl-mongodb available for Code Snippets tests. Previously Code Snippets were expecting the binary in ./bin directory, but this logic was lost when the kubectl-mongodb build process was changed.

mongodb-kubernetes/scripts/evergreen/build_multi_cluster_kubeconfig_creator.sh

Lines 38 to 40 in d40621c

	mkdir -p bin || true
	cp docker/mongodb-kubernetes-tests/multi-cluster-kube-config-creator bin/kubectl-mongodb || true
	cp bin/kubectl-mongodb "${WORKDIR}/bin/kubectl-mongodb" || true

This PR brings back this copy procedure to make Code Snippets tests work. Additionally changed the logic of download_multi_cluster_binary evergreen function and now it only downloads single binary matching platform provided - there is no need to download all platform variants.

Proof of Work

Passing CI and run the test locally:

(venv) ➜ mongodb-kubernetes git:(maciejk/ar-fix-kubectl-plugin-location) ✗ scripts/dev/run_python.sh scripts/release/kubectl_mongodb/download_kubectl_plugin.py --build-scenario staging --version b4789443 --platform linux/amd64 INFO 2025-10-31 13:05:44,644 [download_kubectl_plugin] Downloading s3://mongodb-kubernetes-staging/kubectl-mongodb/b4789443/kubectl-mongodb_linux_amd64 to docker/mongodb-kubernetes-tests/multi-cluster-kube-config-creator_amd64 INFO 2025-10-31 13:05:46,472 [download_kubectl_plugin] Successfully downloaded artifact to docker/mongodb-kubernetes-tests/multi-cluster-kube-config-creator_amd64 and bin/kubectl-mongodb 

Checklist

• Have you linked a jira ticket and/or is the ticket in the title?
• Have you checked whether your jira ticket required DOCSP changes?
• Have you added changelog file?
  • use skip-changelog label if not needed
  • refer to Changelog files and Release Notes section in CONTRIBUTING.md for more details

[github-actions]

⚠️ (this preview might not be accurate if the PR is not rebased on current master branch)

MCK 1.6.0 Release Notes

New Features

• MongoDBCommunity: Added support to configure custom cluster domain via newly introduced spec.clusterDomain resource field. If spec.clusterDomain is not set, environment variable CLUSTER_DOMAIN is used as cluster domain. If the environment variable CLUSTER_DOMAIN is also not set, operator falls back to cluster.local as default cluster domain.
• Helm Chart: Introduced two new helm fields operator.podSecurityContext and operator.securityContext that can be used to configure securityContext for Operator deployment through Helm Chart.

Bug Fixes

• Fixed parsing of the customEnvVars Helm value when values contain = characters.
• ReplicaSet: Blocked disabling TLS and changing member count simultaneously. These operations must now be applied separately to prevent configuration inconsistencies.

Other Changes

• kubectl-mongodb plugin: cosign, the signing tool that is used to sign kubectl-mongodb plugin binaries, has been updated to version 3.0.2. With this change, released binaries will be bundled with .bundle files containing both signature and certificate information. For more information on how to verify signatures using new cosign version please refer to -> https://github.com/sigstore/cosign/blob/v3.0.2/doc/cosign_verify-blob.md