python: pre-install dependencies during virtual environment setup

### Describe the feature

Hi,

Wouldn't it be nice to have the dependencies pre-installed when a cdk app is created at first under the Python Language? The offered virtual-env would then have the app already staged for testing.

### Use Case

I think that this would just enhance the overall workflow of the app minimizing a bit of effort.

### Proposed Solution

A change within the `init.ts` - `postInstallPython` function, one can just add in the call to Python's ENV with regards to the same.

### Other Information

_No response_

### Acknowledgements

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

### CDK version used

2.60.0

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

Mac OS

Start in init.ts at the postInstallPython function and trace how the Python virtual environment is created during CDK app initialization. Determine how the app's dependencies are installed into that environment, then verify that a newly created Python app is already staged for testing.

Written by the indexing model from the issue text.