Restore azuredeploy.json for Key Vault quickstart samples

[msmbaldwin]

Re-adds azuredeploy.json (compiled from main.bicep) for the four Key Vault quickstart samples that lost the file during the recent RBAC modernization PRs:

• Update key-vault-create template to use RBAC instead of access policies #14704 — key-vault-create
• Update key-vault-secret-create template to use RBAC instead of access policies #14705 — key-vault-secret-create
• Add key-vault-key-create template #14706 — key-vault-key-create
• Add key-vault-certificate-create template #14707 — key-vault-certificate-create

Why was it deleted?

During the original PRs, azuredeploy.json was removed under the (incorrect) assumption that CI would regenerate the compiled JSON from main.bicep automatically. AQT doesn't do that — both files are expected to be committed by the contributor, and the "Deploy to Azure" / "Visualize" buttons in each README.md link directly to azuredeploy.json. Restoring the file fixes those buttons.

How was it generated?

Each azuredeploy.json was produced by az bicep build against the corresponding main.bicep already on master. No template logic changes.

[msmbaldwin]

Closing — the AQT pipeline rejects multi-folder PRs. Splitting into four separate PRs (one per sample folder).