feat: consistency group stop replication

[BigBlackWolf]

Description

Sample for stopping replication consistency group. Documentation reference: https://cloud.google.com/compute/docs/disks/async-pd/manage-replication?authuser=0#stop_replication_for_a_consistency_group

To recreate the conditions, in which it would work, there are many dependencies on other snippets in tests. Currently it is dependant on PR #4586

Checklist

• I have followed Contributing Guidelines from CONTRIBUTING.MD
• Tests pass: go test -v ./.. (see Testing)
• Code formatted: gofmt (see Formatting)
• Vetting pass: go vet (see Formatting)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved