[AWS::MediaLive::Channel] - [BUG] - input attachment issue during stack update

### Name of the resource

AWS::MediaLive::Channel

### Resource Name

_No response_

### Issue Description

During CloudFormation stack update, adding new or updating existing input attachment fails.
```
inputId=1047120 is already attached (Service: AWSMediaLive; Status Code: 409; Error Code: ConflictException; Request ID: b0113a97-c361-4e83-bc62-1748f450463f; Proxy: null)
```
No issue updating manually from the AWS Console or via AWS CLI commands

### Expected Behavior

Support adding/updating input attachment via CloudFormation stack updates.

### Observed Behavior

CloudFormation attempts make CREATE api call instead of UPDATE

### Test Cases

Create AWS::MediaLive::Channel with 2 input attachment
1. Try to update one of the attachment
2. Try to add a 3rd attachment

### Other Details

_No response_

Start with the AWS::MediaLive::Channel update path and reproduce the two listed cases: changing an existing input attachment and adding a third. Compare the CloudFormation behavior with the stated AWS Console or CLI behavior; done means stack updates support both attachment changes without the input-already-attached conflict.

Written by the indexing model from the issue text.