CDKv2: `DockerImageAsset` need to execute command before `docker build` / `cdk-asset`

### Describe the feature

I need to execute a shell command before executing `cdk-asset` (that triggers `docker build`) within the generated `CodeBuildAction`.

### Use Case

Preparing the environment for the `docker build` as it otherwise fails.

### Proposed Solution

Add a property to `DockerImageAssetProps`:
```
export interface DockerImageAssetProps extends DockerImageAssetOptions {
/**
* The directory where the Dockerfile is stored
*
* Any directory inside with a name that matches the CDK output folder (cdk.out by default) will be excluded from the asset
*/
readonly directory: string;

// New
prepareCommands : []string;
}

```

These prepareCommands will then be added to the `CodeBuildStep` that executes the `docker build`:

https://github.com/aws/aws-cdk/blob/244135b333007adc1188f0ad8690be4e7526353d/packages/%40aws-cdk/pipelines/lib/codepipeline/codepipeline.ts#L687

### Other Information

Hacky workaround: preprocess generated Cloudformation template using shell scripts after `cdk synth`.

### Acknowledgements

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

### CDK version used

v2

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

not relevant

Read packages/@aws-cdk/pipelines/lib/codepipeline/codepipeline.ts around line 687 and trace how DockerImageAssetProps reaches the generated CodeBuildStep. Define the prepareCommands behavior and verify that generated CodeBuild configuration runs those commands before cdk-asset and the Docker build.

Written by the indexing model from the issue text.