Separate test code for modules with associated testkit to eliminate dependency cycle

[metasim]

Overview

The latest version of IntelliJ no longer handles previous workarounds to handle dependency cycle between a module's test scope and it's test-kit.

For example, sbt sees this:

raster / Test +-> raster-testkit / Compile --> raster / Compile
              |                                ^
              +--------------------------------+

but IntelliJ sees this:

raster / {Test|Compile} --> raster-testkit / Compile --+
                   ^                                   |
                   ------------------------------------+     

[pomadchin]

Closing it for now, I feel like to start this PR from scratch will be an easier lift. I feel like there may be another way to solve it?