Add Testing Framework

[TamimEhsan]

This PR aims to add a minimal testing framework with some example tests without altering the main repo structure. Google Test is used for the overall testing and mocking mechanism.

The current workflow will remain same. To test run

# Create the folders
mkdir build bin
cd build
# Build executables
cmake .. -DRABITQ_BUILD_TESTS=ON
make
# Run all the tests
ctest

Please feel free to modify any files or suggest modifications.