(integ-runner-alpha): (Support setting custom test timeout)

### Describe the feature

Currently, the custom resource Lambda function that does assertions has a default timeout of 2 mins. Further, there does not seem to be a way to specify a higher timeout. This functionality would be really useful in leveraging the full 15 min timeout of Lambda functions.

### Use Case

We have some tests that we'd like to run using CDK integ-runner, but the tests need more than 2 mins.

### Proposed Solution

Support some option named `timeout` or such as shown below.

**Option #1**
```
test.assertions
.invokeFunction({
functionName: functionName,
timeout:
})
.expect(
ExpectedResult.objectLike({
StatusCode: 200,
Payload: "null",
})
);
```

**Option #2**

```
const test = new IntegTest(app, "TestName", {
testCases: [stackUnderTest],
timeout:
});
```

### Other Information

_No response_

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### CDK version used

^2.63.2

### Environment details (OS name and version, etc.)

MacOS Monterey 12.5 (irrelevant to current issue)

Start by tracing the integ-runner-alpha custom resource Lambda used by invokeFunction and IntegTest, focusing on where the two-minute assertion timeout is set. Compare both proposed timeout entry points and verify the completed behavior with an integ-runner test that can use a longer timeout within the Lambda limit.

Written by the indexing model from the issue text.