Add support for regional VPC Endpoints in STS and SQS api calls

[dlpzx]

Is your idea related to a problem? Please describe.
This enhacement is only relevant if VPC endpoints are created outside of data.all and those endpoints are regional and we are using the VPC facing architecture. For some of these VPC endpoints (SQS and STS) we need to explictly specify the endpoint url for the api calls to the service. Otherwise it tries to reach the global endpoint which is not reachable, resulting in failure of the creation of environments and other functionalities that use STS or SQS in the backend.

This issue is described here: boto/boto3#1859

Describe the solution you'd like
data.all to route these api calls independently from the type of endpoints used