Provide for pass-through access to http endpoint of deployed application

[corneil]

Problem description:
Interaction with the underlying platform is needed to obtain the address in order to properly interact with the running application.

Solution description:
Provide an endpoint that provides a proxy to the application by name and optionally instance number.
Example url can be runtime/apps/{appId}/http or runtime/apps/{appId}/instances/{instanceId}/http

This endpoint should provide for all HTTP methods.
In order to provide backwards compatibility runtime/apps/{appId}/instances/{instanceId}/post will map to runtime/apps/{appId}/instances/{instanceId}/http

Potential implementation:
Embed Spring Cloud Gateway
Search execution status when route is unknown and cache the results.
Remove entries from cache when application is destroyed or SCG connection/retries fail a certain amount of times.