Analysis: Analyse using `parallel` runners for E2E Test Parallelization

This issue is to analyse if we can use parallel CI runners to run our E2E testsuite in parallel.

https://docs.gitlab.com/ee/ci/yaml/#parallel

Understand how Knapsack is used for rspec-mysql job in gitlab-ce - https://gitlab.com/gitlab-org/gitlab-ce/blob/master/.gitlab/ci/rails.gitlab-ci.yml#L151