aws-cdk-lib: significantly more memory used as module than commonjs

### Describe the bug

```
~/projects/cdk-test » node --expose-gc test.mjs
HEAP 17.45mb RSS 111.25mb EXT 2.03mb
~/projects/cdk-test ∷ node --expose-gc test.cjs
HEAP 2.91mb RSS 43.34mb EXT 1.07mb
```

test.mjs and .cjs are the same except `import 'aws-cdk-lib` vs `require('aws-cdk-lib)`.

I see similar differences when importing `aws-cdk-lib/core` or `aws-cdk-lib/aws-lambda`.
I don't see similar issues with other large libraries (like @aws-sdk/client-ec2)

### Regression Issue

- [ ] Select this option if this issue appears to be a regression.

### Last Known Working CDK Version

_No response_

### Expected Behavior

Similar memory use between ESM and CJS

### Current Behavior

importing cdk uses more memory than requiring it.

### Reproduction Steps

```
// test.cjs
require('aws-cdk-lib')
const MB = 1024 * 1024

function mb(n) {
return (n / MB).toFixed((2))
}
global.gc?.()
const mem = process.memoryUsage()
console.error(`HEAP ${mb(mem.heapUsed)}mb RSS ${mb(mem.rss)}mb EXT ${mb(mem.external)}mb`)
```
```
// test.mjs
import 'aws-cdk-lib'
const MB = 1024 * 1024

function mb(n) {
return (n / MB).toFixed((2))
}
global.gc?.()
const mem = process.memoryUsage()
console.error(`HEAP ${mb(mem.heapUsed)}mb RSS ${mb(mem.rss)}mb EXT ${mb(mem.external)}mb`)
```

```
~/projects/cdk-test » mise exec node@18 -- node test.mjs
HEAP 21.22mb RSS 84.24mb EXT 1.49mb
~/projects/cdk-test ∷ mise exec node@18 -- node test.cjs
HEAP 4.12mb RSS 40.49mb EXT 0.18mb

~/projects/cdk-test ∷ mise exec node@22 -- node test.mjs
HEAP 27.54mb RSS 110.08mb EXT 2.03mb
~/projects/cdk-test ∷ mise exec node@22 -- node test.cjs
HEAP 3.37mb RSS 43.00mb EXT 1.07mb
```

test.mjs uses significantly more heap and rss

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

N/A

### Framework Version

2.173.2

### Node.js Version

18, 20, 22

### OS

Arch Linux

### Language

TypeScript

### Language Version

N/A (JavaScript)

### Other information

_No response_

Start by running the provided test.mjs and test.cjs reproductions with the listed Node.js versions and compare process.memoryUsage() after garbage collection. Investigate loading aws-cdk-lib, aws-cdk-lib/core, and aws-cdk-lib/aws-lambda through ESM versus CommonJS; done means identifying and reducing the unexplained memory difference, with regression coverage for the measured behavior.

Written by the indexing model from the issue text.