Add testing framework

[mcopik]

We need a custom system to execute integration and system tests without mocking.

• [ ] Add device configuration (#1)
• [ ] Add user-based configuration of testing endpoints
• [x] Integrate gtest with CMake
• [ ] Add test: basic allocation
• [ ] Add test: random-based allocation
• [ ] Add test: simple invocation
• [ ] Add test: warm invocations
• [ ] Add test: async invocations
• [ ] Add test: parallel invocations