This diff is a part of the flat diffs stack to transform the current Tunnelbroker project into a Rust app by calling the current C++ codebase from Rust. The related transition task is [[ https://linear.app/comm/issue/ENG-1072 | ENG-1072 ]].
This diff moves the current `CMakeLists.txt` file into the gtest `test` directory and it's reduced to build only the test app for unit testing purposes only.
Related Linear task and discussion: [[ https://linear.app/comm/issue/ENG-2083/changing-the-tunnelbroker-project-structure-to-be-a-rust-app#comment-c9252d58 | ENG-2083 ]]
**CI Notice:**
The CI will fail on these diffs until the end of the stack with the changes to CI build commands. This stack will be landed all in one to prevent CI from failing on diffs out of this stack.