Replace uses of environment image with runtime image

[dgerd]

In what area(s)?

/area API
/area autoscale
/area build
/area monitoring
/area networking
/area test-and-release

Describe the feature

The runtime test image should have all of the necessary functionality to replace uses of the environment test image. This should allow us to clean up a bunch of test code, reduce the number of test images, and reduce duplication.