[Key Vault Admin] Pre-release work

[sadasant]

The keyvault-admin is currently only the generated code. This issue is to track the work needed to make this client be on par with the other Key Vault clients.

• Add the convenience layer.
• Add the tests.
• Add the samples.
• Review the API and documentation.
• Make sure things work on CI.

Focusing the work this way will make it easier to address:

• [keyvault-admin] Support Role-based Access Control (RBAC) for data plane via new KeyVaultAccessControlClient [keyvault-admin] Support Role-based Access Control (RBAC) for data plane via new KeyVaultAccessControlClient #7279
• [keyvault-admin] Implement a new client with vault backup and restore operations [keyvault-admin] Implement a new client with vault backup and restore operations #9215

Regarding the convenience layer

Look for other clients for reference. For example:

• .Net: https://github.com/Azure/azure-sdk-for-net/tree/master/sdk/keyvault/Azure.Security.KeyVault.Administration

Heath mentioned that they don't have a KeyVaultAdmin client, but one KeyVaultAccessControlClient and another KeyVaultBackupClient.

[sadasant]

Done! Closing!