fix: add validation for useAzureIdentity in azureKeyVaults section

Radix Webhook RadixApplication validator should validate that the component's common or environmentConfig has configured `identity.azure.clientId` when `azureKeyVaults.useAzureIdentity` is set to true.

This is currently not validated, which leads to sync failure for RadixDeployments when trying to setup AzureKeyVault integration with workload identity:

```
Deployment Error
failed to provision secrets: failed to sync secrets for component {componentName}: failed to build secret provider class parameters for application {appName}, component {component}: missing Azure identity when using Azure Key Vault {keyVault} with Azure identity
```