[Key Vault] Run samples in test pipelines

[mccoyp]

New tracking issue for #23892.

Per the instructions in this document, we should configure our live test pipelines to run repo samples in order to catch bugs and breaking changes. The bulk of this change should only involve updating environment variable references (using the variable names we get from New-TestResources.ps1).

More investigation may be needed in scenarios like backup/restore in azure-keyvault-administration, where operations should be done with Managed Identity where possible. If this can't be done in test pipelines, we may want to either use SAS tokens, or (since that could encourage users to use SAS tokens when MI is preferred) skip these samples in pipelines.