Bumping version to 2.2.0

[fcostaoliveira]

Summary

This PR bumps the version from 2.1.4 to 2.2.0 to include recent feature additions and improvements.

New Features on 2.2.0 (the reason for the minor bump)

• Added option to print and save all results when running multiple test iterations (Add option to print and save all results, when performing multiple test iterations #298 by @Yuval-Ariel).
• Initial support for keys following Zipfian distribution (Initial support for keys following zipfian #166 by @lfsu-ali).
• Enabled Zipfian key distribution for arbitrary commands (Enabled Zipfian key distribution for arbitrary commands. #314 by @filipecosta90).
• Added --uri flag to memtier_benchmark (compatible with redis-cli and redis-benchmark URI parsing) (Add URI flag to memtier_benchmark (compatible with redis-cli and redis-benchmark parsing) #311 by @filipecosta90).

Improvements & Fixes

• Improved deconstruction performance of imported_keylist (improve the performance of imported_keylist deconstruction #239 by @DarrenJiang13).
• Fixed request handling issue (Fix request #307 by @maxb-io).
• Removed ubuntu-20.04 from build matrix following GitHub deprecation (Remove ubuntu-20.04 from build-build matrix due to GH removal #309 by @paulorsousa).
• Added macOS installation instructions via Homebrew (Add macOS installation instructions via Homebrew #313 by @paulorsousa).