DataCaptureConfigSummary.kms_key_id is required but should be Optional — Endpoint.get() fails

**PySDK Version**
- [X] PySDK V3 (3.7.0)

**Describe the bug**

`DataCaptureConfigSummary.kms_key_id` in `sagemaker-core` is defined as a required field, but the SageMaker `DescribeEndpoint` API omits `KmsKeyId` from the response when no customer-managed KMS key is configured. This causes `Endpoint.get()` to fail with a Pydantic `ValidationError` on any endpoint that has data capture enabled without a KMS key.

The input shape `DataCaptureConfig` correctly marks `kms_key_id` as `Optional[StrPipeVar] = Unassigned()`, but the output shape `DataCaptureConfigSummary` has it as required: `kms_key_id: StrPipeVar`.

**To reproduce**

```python
"""
Reproduction: Endpoint.get() fails on endpoints with data capture enabled but no KMS key.

Prerequisites:
pip install sagemaker boto3
An existing SageMaker realtime endpoint with data capture enabled and NO KMS key.
"""
import boto3

session = boto3.Session()
sm = session.client("sagemaker")

# Replace with your endpoint that has data capture enabled (no KMS key)
endpoint_name = "my-endpoint"

# Step 1: Verify the API response omits KmsKeyId
desc = sm.describe_endpoint(EndpointName=endpoint_name)
dc = desc.get("DataCaptureConfig", {})
print(f"EnableCapture: {dc.get('EnableCapture')}") # True
print(f"KmsKeyId present: {'KmsKeyId' in dc}") # False

# Step 2: This fails with ValidationError
from sagemaker.core.resources import Endpoint

endpoint = Endpoint.get(endpoint_name, session=session)
```

**Expected behavior**

`Endpoint.get()` should succeed. `KmsKeyId` is optional in the SageMaker API — endpoints can have data capture enabled without a customer-managed KMS key (S3 uses default encryption in that case).

**Screenshots or logs**

```
ValidationError: 1 validation error for Endpoint
data_capture_config.kms_key_id
Field required [type=missing, input_value={'enable_capture': True,
...'destination_s3_uri': 's3://...'}, input_type=dict]
For further information visit https://errors.pydantic.dev/2.12/v/missing
```

**System information**
- **SageMaker Python SDK version**: 3.7.0 (sagemaker-core 2.7.1)
- **Framework name (eg. PyTorch) or algorithm (eg. KMeans)**: N/A — applies to any endpoint with data capture
- **Framework version**: N/A
- **Python version**: 3.12 / 3.13
- **CPU or GPU**: CPU
- **Custom Docker image (Y/N)**: N

**Additional context**

The fix is a one-line change in the auto-generated `DataCaptureConfigSummary` class in `sagemaker/core/shapes/shapes.py`:

```python
# Current (broken) — required field:
kms_key_id: StrPipeVar

# Fix — optional, matching the input shape DataCaptureConfig:
kms_key_id: Optional[StrPipeVar] = Unassigned()
```

Workaround (monkey-patch at import time):
```python
from sagemaker.core.shapes.shapes import DataCaptureConfigSummary
from sagemaker.core.utils.utils import Unassigned

DataCaptureConfigSummary.model_fields["kms_key_id"].default = Unassigned()
DataCaptureConfigSummary.model_rebuild(force=True)
```

Mở sagemaker/core/shapes/shapes.py và so sánh DataCaptureConfigSummary với DataCaptureConfig đầu vào. Xác minh thay đổi bằng bản tái hiện Endpoint.get() được cung cấp; hoàn tất nghĩa là một endpoint đã bật thu thập dữ liệu và không có khóa KMS có thể được phân tích mà không gặp Pydantic ValidationError.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.