Expose DockerImage information with EnforcedLocalMachine Builds

Currently, EnforcedLocalMachine is just another valid ExecutionRuntime like LocalMachine or any custom created one. This should be changed to be an additive flag, e.g.

Chrome + NET462 + Debug + x86 + NoDB + Win_NET48 + EnforcedLocalMachine

Indicating "The tests itself should not be run inside a docker container, but we want to expose docker image information upstream so it can be used for other build steps in this test run"