AssetStaging: `DockerVolume` uses Bind Mount with BundlingFileAccess set to VOLUME_COPY

### Describe the bug

Setting `bundling.bundlingFileAccess: BundlingFileAccess.VOLUME_COPY` in AssetStaging still uses bind mounts for additional volumes created through `bundling.volumes`. The language in the docs does not make this explicitly clear, and leaves no good way to use additional volumes in envs where bind mounts are unavailable (e.g. DinD)

### Regression Issue

- [ ] Select this option if this issue appears to be a regression.

### Last Known Working CDK Version

_No response_

### Expected Behavior

When using `BundlingFileAccess.VOLUME_COPY`, I expect all volumes to use the volume copy behaviour

### Current Behavior

Additional volumes use bind mounts regardless of `bundlingFileAccess` setting

### Reproduction Steps

Use AssetStaging with BundlingFileAccess.VOLUME_COPY set and an additional volume mounted
```typescript
const codeAsset = new AssetStaging(this, 'CodeAsset', {
sourcePath: path.resolve('mule'),
exclude: ['target/*', 'bin/*', '*.class', '*.jar'],
bundling: {
image: DockerImage.fromRegistry('public.ecr.aws/docker/library/alpine'),
bundlingFileAccess: BundlingFileAccess.VOLUME_COPY,
volumes: [{
hostPath: '~/.m2',
containerPath: '/root/.m2',
}],
},
});
```

### Possible Solution

Rewrite the `AssetStaging` class to mount all volumes via the VOLUME_COPY mechanism instead of only the input and output. Alternately, extend DockerVolume as suggested in #20601 to allow each volume provided to choose its binding type (bind mount, volume copy, existing volume)

### Additional Information/Context

_No response_

### CDK CLI Version

2.174.0 (build 9604329)

### Framework Version

_No response_

### Node.js Version

v20.13.1

### OS

Ubuntu

### Language

TypeScript

### Language Version

_No response_

### Other information

_No response_

Start by tracing AssetStaging and DockerVolume handling for bundling.volumes, comparing the additional-volume path with BundlingFileAccess.VOLUME_COPY. Reproduce the issue with the TypeScript example and inspect the existing volume-copy behavior. Done means the documented and implemented volume behavior matches the selected access mode, including additional volumes.

Written by the indexing model from the issue text.