Create a "DefaultStackName" Section

### Name of the resource

Other

### Resource name

Template anatomy

### Description

I'd like to include a Default Stack Name in the template and allow it to use some Pseudo Parameters

For example:

``` YAML
Description: SampleStack with a default stackname

DefaultStackName:
!Sub: "MyStack-$(AWS::Account}-${AWS::Region}"

Resources:
<.....>

```

Some of the benefits would be:

1. Consistency in naming when deploying to multiple accounts and regions.
2. Improved development speed and testing of new templates by having one less thing to type.

### Other Details

Here are a couple of other people that have requested this feature:

https://stackoverflow.com/questions/51828313/is-it-possible-to-statically-specify-awsstackname-inside-a-cloudformation-temp

https://www.reddit.com/r/aws/comments/oix0wj/specify_stack_name_within_cloudformation_template/

Start with the CloudFormation template anatomy described in the issue and review the linked requests for the expected DefaultStackName behavior. No repository files, tests, or entry points are named; done would mean defining and documenting a template section that accepts pseudo parameters and provides a default stack name.

Written by the indexing model from the issue text.