feat(toolkit): Stop creating 'empty' stacks (#779)

When deploying a stack for the first time in an environment, the toolkit
would until now create the stack with a dummy resource (a
WaitConditionHandle), so it could then prepare & execute a ChangeSet.
It turns out it is possible to use a CHangeSet to create a stack as well,
by passing a CHangeSetType parameter to the CreateChangeSet API. This
commit changes the toolkit to use this feature, so that the first
deployment of a stack is going to behave a lot more consistently compared
to the subsequent update deployments. It also removes quite a bit of code.

packages/aws-cdk/lib/api/deploy-stack.ts

@@ -41,17 +41,14 @@ export async function deployStack(stack: cxapi.SynthesizedStack,
     const cfn = await sdk.cloudFormation(stack.environment, Mode.ForWriting);
     const bodyParameter = await makeBodyParameter(stack, toolkitInfo);
 
-    if (!await stackExists(cfn, deployName)) {
-        await createEmptyStack(cfn, deployName, quiet);
-    } else {
-        debug('Stack named %s already exists, updating it!', deployName);
-    }
+    const update = await stackExists(cfn, deployName);
 
     const changeSetName = `CDK-${executionId}`;
-    debug('Attempting to create ChangeSet %s on stack %s', changeSetName, deployName);
+    debug(`Attempting to create ChangeSet ${changeSetName} to ${update ? 'update' : 'create'} stack ${deployName}`);
     const changeSet = await cfn.createChangeSet({
         StackName: deployName,
         ChangeSetName: changeSetName,
+        ChangeSetType: update ? 'UPDATE' : 'CREATE',
         Description: `CDK Changeset for execution ${executionId}`,
         TemplateBody: bodyParameter.TemplateBody,
         TemplateURL: bodyParameter.TemplateURL,
@@ -87,24 +84,6 @@ async function getStackOutputs(cfn: aws.CloudFormation, stackName: string): Prom
     return result;
 }
 
-async function createEmptyStack(cfn: aws.CloudFormation, stackName: string, quiet: boolean): Promise<void> {
-    debug('Creating new empty stack named %s', stackName);
-
-    const template = {
-        Resources: {
-            WaitCondition: {
-                Type: 'AWS::CloudFormation::WaitConditionHandle'
-            }
-        }
-    };
-
-    const response = await cfn.createStack({ StackName: stackName, TemplateBody: JSON.stringify(template, null, 2) }).promise();
-    debug('CreateStack response: %j', response);
-    const monitor = quiet ? undefined : new StackActivityMonitor(cfn, stackName, undefined, 1).start();
-    await waitForStack(cfn, stackName);
-    if (monitor) { monitor.stop(); }
-}
-
 /**
  * Prepares the body parameter for +CreateChangeSet+, putting the generated CloudFormation template in the toolkit-provided
  * S3 bucket if present, otherwise using in-line template argument. If no +ToolkitInfo+ is provided and the template is