[Testing] Implement a clean way to get the deployed app URL

[meltsufin]

No description provided.

[jmcc0nn3ll]

This would allow us to do away with the split IntegrationTest setup, LocalIntegrationTest/RemoteIntegrationTest. Currently the only fundamental difference between the two is this URI, localhost: for local and the remote URI combining service id, project id and version.

Now there will likely be differences in tests soon we are currently able to express now, but a cleaner approach down the road might be to use test scoped annotations instead of the <includes/excludes> in the pom.xml.

tl;dr easy access to the URI means we can re-evaluate some testing structure

[joakime]

This seems similar to the enhancement request at GoogleCloudPlatform/app-maven-plugin/issues/86

[jmcc0nn3ll]

That's the one I was looking for, thanks @joakime