custom-resource: support isComplete handler for AwsCustomResource

### Describe the feature

Please add the isCompleteHandler functionality to AwsCustomResource also.

Thank you for your consideration!

As suggested by @hoegertn

### Use Case

When I make use of `AwsCustomResource` to `ModifyVpnTunnelOptions`, I would not know when the modification completed. As I need to modify both tunnels, adding a dependency would not help. The second `AwsCustomResource` to run `ModifyVpnTunnelOptions` would start and fail with an error as the VPN is in state "modifying".

So I would end up creating a `CustomResource`, so I can make use of the `isCompleteHandler`.

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

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

### CDK version used

2.150.0

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

Darwin mbp.local 23.5.0 Darwin Kernel Version 23.5.0: Wed May 1 20:19:05 PDT 2024; root:xnu-10063.121.3~5/RELEASE_ARM64_T8112 arm64

Start by locating AwsCustomResource in the aws-cdk repository and compare it with the CustomResource path that already supports isCompleteHandler. Trace how asynchronous completion is handled, then verify that AwsCustomResource can wait for operations such as ModifyVpnTunnelOptions to finish before another resource runs.

Written by the indexing model from the issue text.