Adding `AdaptResourceIfExists` or `AutoImportResourceIfExists` Flag to CFN Resources

### Name of the resource

ALL

### Resource name

ALL

### Description

As name of feature says, I would like to see CloudFormation automate import of resource if it is already exist without need to do it manually via AWS Management Console.

This will save user time in many cases like:
1. User will not need to manually/scripting clean already existing resources that left behind of failed deployment and reuse it in next trail after fixing issue.
2. Some resources are time expensive to create from beginning. This feature will allow user to reuse resources that already exist especially for testing purposes.
3. Simply customer want to ignore AlreadyExistException on resource that hold specific name.

The issue names no repository files, tests, or entry points. Start by reviewing the current CloudFormation resource import workflow described in the issue and define how an all-resource AdaptResourceIfExists or AutoImportResourceIfExists flag should behave; done requires an agreed scope and design for existing resources, failed deployments, and AlreadyExistException cases.

Written by the indexing model from the issue text.