Make response parameters of makeIntegrationResponsesAllowCors customizable

[kikuomax]

Users may want to customize values in response parameters set by makeIntegrationResponsesAllowCors. It sets the following response parameters for now,

• Access-Control-Allow-Origin: *
• Access-Control-Allow-Headers: equivalent to aws_apigateway.Cors.DEFAULT_HEADERS
• Access-Control-Allow-Methods: equivalent to aws_apigateway.Cors.ALL_METHODS