chore(core): show counts of resources when stack is overflowing (#20398)

This makes it easier to diagnose why you are overlowing the maximum of
500 resources.


----

### All Submissions:

* [ ] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md)

### Adding new Unconventional Dependencies:

* [ ] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/master/INTEGRATION_TESTS.md)?
	* [ ] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: rix0rrr

packages/@aws-cdk/core/lib/stack.ts

@@ -791,7 +791,8 @@ export class Stack extends CoreConstruct implements ITaggable {
       const numberOfResources = Object.keys(resources).length;
 
       if (numberOfResources > this.maxResources) {
-        throw new Error(`Number of resources in stack '${this.node.path}': ${numberOfResources} is greater than allowed maximum of ${this.maxResources}`);
+        const counts = Object.entries(count(Object.values(resources).map((r: any) => `${r?.Type}`))).map(([type, c]) => `${type} (${c})`).join(', ');
+        throw new Error(`Number of resources in stack '${this.node.path}': ${numberOfResources} is greater than allowed maximum of ${this.maxResources}: ${counts}`);
       } else if (numberOfResources >= (this.maxResources * 0.8)) {
         Annotations.of(this).addInfo(`Number of resources: ${numberOfResources} is approaching allowed maximum of ${this.maxResources}`);
       }
@@ -1357,6 +1358,18 @@ export interface ExportValueOptions {
   readonly name?: string;
 }
 
+function count(xs: string[]): Record<string, number> {
+  const ret: Record<string, number> = {};
+  for (const x of xs) {
+    if (x in ret) {
+      ret[x] += 1;
+    } else {
+      ret[x] = 1;
+    }
+  }
+  return ret;
+}
+
 // These imports have to be at the end to prevent circular imports
 import { CfnOutput } from './cfn-output';
 import { addDependency } from './deps';