(@aws-cdk/integ-tests-alpha): Verifying snapshot doesn't read values from cdk.context.json

### Describe the bug

When running an integration test with `integ-runner` the verification of the snapshot fails if the integration test contains a `VPC.fromLookup(...)`. The snapshot verification show a difference in the VpcId with the new value being the default VpcID dummy value of `vpc-12345`.

### Expected Behavior

The `integ-runner` would read the VpcId from the `cdk.context.json`.

### Current Behavior

```
#> integ-runner integ.bug.ts

Verifying integration test snapshots...

CHANGED integ.bug 5.097s
Resources
[~] AWS::EC2::SecurityGroup sgxxxxxxx replace
└─ [~] VpcId (requires replacement)
├─ [-] vpc-xxxxxxxxxxxxx
└─ [+] vpc-12345

Snapshot Results:

Tests: 1 failed, 1 total

```

As shown in the output above, the VpcId falls back to the default value of `vpc-12345`.

### Reproduction Steps

Define the following integration test:
1) run with `integ-runner --update-on-failed` -> this will create the `cdk.context.json` with the lookup values.
2) run with `integ-runner`

```typescript
import * as cdk from 'aws-cdk-lib';
import * as ec2 from 'aws-cdk-lib/aws-ec2';
import * as integ from '@aws-cdk/integ-tests-alpha';

const REGION = 'eu-central-2';
const ACCOUNT = 'SOME_ACCOUNT_ID';
const VPC_ID = 'some existing vpc id';

const app = new cdk.App({
context: {
'@aws-cdk/core:bootstrapQualifier': '',
},
});

const stack = new cdk.Stack(app, 'integBug', {
env: {
account: ACCOUNT,
region: REGION,
},
});

const vpc = ec2.Vpc.fromLookup(stack, 'vpc', {
vpcId: VPC_ID,
});

new ec2.SecurityGroup(stack, 'sg', {
vpc: vpc,
});

new integ.IntegTest(app, 'integTest', {
testCases: [stack],
});
```

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.148.1 (build 283525d)

### Framework Version

_No response_

### Node.js Version

v20.15.0

### OS

Linux

### Language

TypeScript

### Language Version

Typescript (5.5.4)

### Other information

_No response_

Start with the integ.bug.ts reproduction and the integ-runner snapshot-verification path, then compare normal runs with --update-on-failed while checking how cdk.context.json is used. Done means the verification preserves the looked-up VPC ID instead of substituting vpc-12345 and the reproduction no longer reports a false snapshot difference.

Written by the indexing model from the issue text.