API Gateway should be set to regional instead of edge-optimized

[corollari]

By default the API gateway generated by serverless is set to be edge optimized, meaning that, if a cloudfront distribution is added on top of that, api requests will hit cloudfront nodes twice:

Client -> CloudFront distribution (this plugin) -> CloudFront distribution (Edge optimized API gateway) -> API Gateway -> Lambda

This increases the latency of responses and mangles several cloudfront headers such as CloudFront-Viewer-Country, making them useless (see https://stackoverflow.com/questions/46490508/api-gateway-caching-vs-cloudfront).

To fix this, this plugin should change the api gateway resources to be regional instead of edge-optimized.