Add akv token request logic (#9556)

Add support for running queries that require a decryption key from Azure Key Vault when using Always Encrypted.

src/sql/platform/accounts/common/interfaces.ts

@@ -45,7 +45,8 @@ export interface IAccountManagementService {
 export enum AzureResource {
 	ResourceManagement = 0,
 	Sql = 1,
-	OssRdbms = 2
+	OssRdbms = 2,
+	AzureKeyVault = 3
 }
 
 export interface IAccountStore {