feat(ecs-patterns): allow custom ephemeral storage for ECS Fargate se…

…rvices (aws#29275)

### Issue # (if applicable)

Closes aws#18105.

### Reason for this change

In April 2021, Fargate added support for [requesting additional ephemeral storage](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/fargate-task-storage.html#fargate-task-storage-pv14).

Support for this feature has [been added](aws@f1bf935#diff-dcfbc499b4d3c10afcd4e63ad0e4ecc54df2464e45af67f1fdae69d3fa2d43a0) to the aws-ecs package, but is still not supported by the aws-ecs-patterns package.

### Description of changes

This code change adds an optional field `ephemeralStorageGiB` in `packages/aws-cdk-lib/aws-ecs-patterns/lib/base/fargate-service-base.ts`, after other fields like `cpu` and `memoryLimitMiB`.

### Description of how you validated changes

Added unit tests and new integration tests.
Created a simple CDK application with the new constructs, and verified that it synthesized and deployed correctly.

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*