Add benchmark modules

[anthonycr]

Created 2 modules with benchmarks for mockk and mockingbird, benchmark-mockingbird and benchmark-mockk as the control benchmark.

Currently, mockingbird benchmark runs using gradle-profiler for an average of 3610ms, while mockk runs with an average of 3263ms. This discrepancy is due to the lack of any KSP code generation running on the mockk benchmark. I did some preliminary testing, and it showed that if a KSP is added to the mockk, for example, if dagger is added to both benchmarks, the discrepancy is non existent and mockingbird performs slightly better. I'm going to leave the benchmarks without this for now.

In order to run the benchmarks, select a folder that you want to run the benchmark in, and then run

 gradle-profiler --benchmark --project-dir /Path/To/Mockingbird clean :benchmark-mockk:test

and

 gradle-profiler --benchmark --project-dir /Path/To/Mockingbird clean :benchmark-mockingbird:test

[anthonycr]

See also #2