Monotonic time

[pboling]

Important background: Monotonic time is the "correct" way to calculate elapsed time in Ruby:
https://blog.dnsimple.com/2018/03/elapsed-time-with-ruby-the-right-way/

• Adds started_at based on the monotonic clock which is guaranteed to always move forward (processor uptime)
• Fixes created_at / timestamp based on Process.clock_gettime(Process::CLOCK_REALTIME), to avoid Time.now stubbing & Timecop issues
• Fixes I am experiencing race condition while using SimpleCov with Parallel_tests #559 (I think)
• Fixes Race Condition in parallel_tests integration: an outdated report may be written #815 (I think)
• Fixes some spec failures in the cucumber suite, due to a bug in Rails, where it failed to require "logger".
• Fixes an out of order condition which results in incompability with turbo_tests - an "almost drop-in" replacement/enhancement of parallel_tests) (see: Simplecov support serpapi/turbo_tests#24) (though there are other major blockers preventing compatibility with turbo_tests)

I do not understand the rubocop failure in CI, because when I run locally there are no violations:

❯ bundle exec rubocop -a
Inspecting 111 files
...............................................................................................................

111 files inspected, no offenses detected

Same result when run with bundle exec rake rubocop as it is in CI.

CC @ilyazub

[pboling]

This is now ready for review @amatsuda @PragTob