fix(ecs): allow ephemeralStorageGiB for Windows Fargate platform version 1.0.0 (#37589)

### Issue # (if applicable)

Closes #37510.

### Reason for this change

`FargateService` currently throws `EphemeralStorageGibFeatureRequires` when `ephemeralStorageGiB` is set and the Fargate platform version is < 1.4.0.

This validation is correct for Linux tasks, but incorrect for Windows tasks: according to the ECS documentation, Windows Fargate supports task ephemeral storage starting with platform version 1.0.0.

### Description of changes

- Added a public getter for `TaskDefinition.runtimePlatform` so `FargateService` can determine the task operating system family.
- Updated `FargateService` validation to only require platform version >= 1.4.0 for `ephemeralStorageGiB` on non-Windows (Linux) tasks.
- Updated the `ephemeralStorageGiB` documentation to reflect the different minimum platform versions for Linux vs. Windows tasks.
- Added a unit test verifying that setting `ephemeralStorageGiB` on a Windows Fargate task definition with platform version 1.0.0 does not fail during synth.

Alternatives considered:
- Removing the validation entirely (rejected: Linux requires 1.4.0+).
- Introducing a separate public API just for the OS family (rejected: `runtimePlatform` already models the required information).

### Describe any new or updated permissions being added

None.

### Description of how you validated changes

- Added a unit test in `packages/aws-cdk-lib/aws-ecs/test/fargate/fargate-service.test.ts` that synthesizes a Windows Fargate service using `platformVersion: VERSION1_0` and `ephemeralStorageGiB`.
- Existing unit test coverage for the Linux restriction (platform version < 1.4.0) remains unchanged.

### 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)

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

Author: rgoltz