[AWS::BedrockAgentCore::Runtime] - [coverage] - Add LoggingConfiguration attribute for CloudWatch Log Group customization

### Name of the resource

Other

### Resource name

AWS::BedrockAgentCore::Runtime

### Description

# Coverage Request for AWS::BedrockAgentCore::Runtime

## Category

**(c) New attribute for an existing resource is desired**

## Resource

`AWS::BedrockAgentCore::Runtime`

## Describe the scope of your request

### Current State

The `AWS::BedrockAgentCore::Runtime` resource automatically provisions a CloudWatch Log Group for runtime logs. However, there is no CloudFormation property to configure or customize this log group.

The auto-created log group has:
- **Retention:** Never expire (indefinite retention)
- **Encryption:** Default service encryption (no customer-managed KMS key)

### Requested New Attribute

Add a new `LoggingConfiguration` property to the `AWS::BedrockAgentCore::Runtime` resource that allows users to either:

1. **Bring Your Own CloudWatch Log Group** - Specify an existing log group ARN
2. **Configure the auto-created log group** - Set retention period and KMS key

### Proposed Property Structure

```yaml
Type: AWS::BedrockAgentCore::Runtime
Properties:
# ... existing properties ...
LoggingConfiguration:
CloudWatchLogGroupArn: String # ARN of existing log group (optional)
RetentionInDays: Integer # Log retention period (optional)
KmsKeyArn: String # Customer-managed KMS key ARN (optional)

### Other Details

_No response_

Start by reviewing the AWS::BedrockAgentCore::Runtime resource definition and its existing CloudWatch logging behavior; the issue names no repository files or tests. Confirm the supported LoggingConfiguration shape and the expected ARN, retention, and KMS-key behavior before determining how the requested coverage should be represented.

Written by the indexing model from the issue text.