[feat] Waiter support

[exoego]

Waiters API definition https://github.com/aws/aws-sdk-js/blob/9b64887b9f6d12b8f87389724aa31bb90651573f/apis/cloudformation-2010-05-15.waiters2.json

TypeScript definition

• API https://github.com/aws/aws-sdk-js/blob/2f0fd56f1c9530c77cd2a59714b91c76a94de76f/clients/cloudformation.d.ts#L458
• WaiterConfiguration interface https://github.com/aws/aws-sdk-js/blob/19a5b5936f2356441d9fc02de2c2ca1409439f54/lib/service.d.ts

[exoego]

This requires literal support #20 for better typing.

  waitFor(state: "changeSetCreateComplete", params: CloudFormation.Types.DescribeChangeSetInput & {$waiter?: WaiterConfiguration}, callback?: (err: AWSError, data: CloudFormation.Types.DescribeChangeSetOutput) => void): Request<CloudFormation.Types.DescribeChangeSetOutput, AWSError>;
  waitFor(state: "changeSetCreateComplete", callback?: (err: AWSError, data: CloudFormation.Types.DescribeChangeSetOutput) => void): Request<CloudFormation.Types.DescribeChangeSetOutput, AWSError>;
  waitFor(state: "typeRegistrationComplete", params: CloudFormation.Types.DescribeTypeRegistrationInput & {$waiter?: WaiterConfiguration}, callback?: (err: AWSError, data: CloudFormation.Types.DescribeTypeRegistrationOutput) => void): Request<CloudFormation.Types.DescribeTypeRegistrationOutput, AWSError>;