ecs: support S3 Files volumes in ECS task definitions

### Describe the feature

The L2 construct for ECS task definitions does not support S3 Files volumes. The L1 CloudFormation constructs for S3 Files volumes already exist, but cannot be utilized by the L2 ECS task defintion.

### Use Case

I want to use S3 Files volumes from ECS task definitions created by CDK.

### Proposed Solution

Added s3FilesVolumeConfiguration property to Volume input and updated supporting code to support populating the field on the L1 construct.

### Other Information

_No response_

### Acknowledgements

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

### AWS CDK Library version (aws-cdk-lib)

aws-cdk-lib@2.250.0

### AWS CDK CLI version

2.1120.0 (build acefbf8)

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

macOS Tahoe 26.4.1

Start at the ECS task-definition L2 Volume input and compare it with the existing L1 S3 Files volume configuration. Trace how current Volume fields populate the L1 construct, then verify that the new property is propagated consistently. Done means CDK-created ECS task definitions can configure S3 Files volumes without breaking existing volume inputs.

Written by the indexing model from the issue text.