Too Many Requests (Service: ApiGateway, Status Code: 429, ...) from AWS::ApiGateway::Model

### Name of the resource

AWS::ApiGateway::Model

### Resource Name

AWS::ApiGateway::Model

### Issue Description

When creating/updating many models (I currently have 114 models of varying sizes, but this error started happening before, at varying intervals) deployment fails with the error:

> Too Many Requests (Service: ApiGateway, Status Code: 429, ...)

### Expected Behavior

It should create the model successfully. For example using exponential backoff to retry the create requests.

### Observed Behavior

The deployment fails with the error:

> Too Many Requests (Service: ApiGateway, Status Code: 429, ...)

### Test Cases

Create tons of API Gateway models, the deployment should not fail. The same should go with updating and removing them.

### Other Details

#588 should have solved this.

Review issue #588 and the AWS::ApiGateway::Model create, update, and delete operations first. Reproduce the failure with many models and inspect how throttling errors are currently handled. Done means deployments retry 429 responses with backoff instead of failing when models are created, updated, or removed.

Written by the indexing model from the issue text.