feat(rds): add RDS db proxy endpoint capabilities

[siddarthkay]

Problem

Ability to view RDS Db Proxy endpoint inputs does not exist.

Solution

This PR adds a new db_proxy_endpoints.go file which queries the AWS Go SDK and implements support for returning RDS ProxyEndpoints.
An entry has also been made to aws.go to make sure rds.ProxyEndpoints is included

Changes Made

fixes #565

How to Test

Apply filter in Dashboard:

• Cloud Provider is AWS
• Cloud Service is RDS DB Proxy endpoint

and you should be able to see RDS ProxyEndpoint resources.

Screenshots

WIP

Checklist

• Code follows the contributing guidelines
• Changes have been thoroughly tested
• Documentation has been updated, if necessary
• Any dependencies have been added to the project, if necessary

Reviewers

[mlabouardy]

thanks a million, @siddarthkay 🚀