feat: create secondary disk sample

[BigBlackWolf]

Description

Snippet demonstrates how to create secondary disk. Documentation reference: https://cloud.google.com/compute/docs/disks/async-pd/configure#create_a_secondary_disk

PRs chain:

1. feat: create secondary disk sample #4513
2. feat: create secondary disk on regional level and with custom guest features #4532
3. feat: start/stop async replication samples #4569

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

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• compute/disks/create_secondary_disk.go:17, tag compute_disk_create_secondary

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