(integ_tests_alpha): Support non-TypeScript tests

### Describe the bug

I have written a simple integration test case to my stack in Python, but I am not able to run it. I used integ-runner and tried with cdk deploy --app "python integration_test.py" but it seems none of them are working. Is this feature available only with ts library?

Many thanks

### Expected Behavior

Able to run my tests.

### Current Behavior

yarn's integ-runner cli uses *ts files to run tests, so with my python code it will not compile

with cdk deploy --app "python integ_tests.py" the stack deployed, but nothing happened

### Reproduction Steps

```
app = App()

stack = Stack(app, "stack",env=default_env)
integ = IntegTest(app, "Integ", test_cases=[stack])

invoke = integ.assertions.invoke_function(
function_name=stack.writer_lambda.function_name
)
invoke.expect(ExpectedResult.object_like({
"Payload": "200"
}))
```

### Possible Solution

_No response_

### Additional Information/Context

_No response_

### CDK CLI Version

2.28.0 (build ba233f0)

### Framework Version

_No response_

### Node.js Version

16.15.1

### OS

Mac OS 12.3.1

### Language

Python

### Language Version

3.9.4

### Other information

_No response_

Start with the integ-runner CLI and the cdk deploy --app path described in the issue, then compare how the shown Python IntegTest is handled versus TypeScript tests. Confirm the supported entry points and identify what must change for a Python integration test to execute its assertions; done means the provided Python example runs successfully.

Written by the indexing model from the issue text.