[aws_eks]: deploying helmcharts requires "chart/chart_asset_url" property which isn't taken into account at all when in OCI flow

### Describe the bug

Currently when passing OCI url to repository property, the lambda's logic doesn't take into account any of mentioned properties, because chart is pulled from path passed by repository + version properties.

### Expected Behavior

chart/chart_asset_url property isn't required when in OCI flow

### Current Behavior

In OCI flow lambda fails with `chart or chartAsset must be specified` when chart/chart_asset_url property isn't provided.

### Reproduction Steps

Deploy like
```
aws_eks.HelmChart(
scope=self.scope,
id="pet-service",
cluster="some-cluster",
repository='oci://xxx.dkr.ecr.us-east-1.amazonaws.com/pet-service',
release='pet-service',
version='1.0.0'
)
```

### Possible Solution

Simply put `chart == None and chart_asset_url == None` validation after the OCI-related logic

### Additional Information/Context

_No response_

### CDK CLI Version

2.38.1 (build a5ced21)

### Framework Version

_No response_

### Node.js Version

v16.14.0

### OS

CentOS

### Language

Python

### Language Version

Python 3.8.5

### Other information

_No response_

Start at the aws_eks.HelmChart OCI flow and reproduce the deployment using the provided Python example with repository, release, and version but no chart or chart_asset_url. Trace when the OCI-related handling occurs, then verify that the missing chart properties are accepted for OCI deployments while the existing error remains for other flows.

Written by the indexing model from the issue text.