[AWS::Pinpoint::PushTemplate] - [Coverage] - Support RawContent property to create push template with raw message type

### Name of the resource

AWS::Pinpoint::PushTemplate

### Resource name

_No response_

### Description

CloudFormation doesn't currently support raw message type via CloudFormation. It always creates with standard message type.

AWS::Pinpoint::PushTemplate - AWS CloudFormation
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-pinpoint-pushtemplate.html

CreatePushTemplate API has request parameter of `RawContent`, but CloudFormation doesn't support the parameter.

Push Notification Template - Amazon Pinpoint
https://docs.aws.amazon.com/pinpoint/latest/apireference/templates-template-name-push.html#templates-template-name-push-schemas

### Other Details

_No response_

Start with the AWS::Pinpoint::PushTemplate CloudFormation documentation and the linked CreatePushTemplate API schema, comparing the existing supported properties with RawContent. Done means the resource accepts RawContent and can create a push template with the raw message type, with coverage verified against the documented API behavior.

Written by the indexing model from the issue text.