Resolve all RuboCop offenses for Sentry Client code and specs

What does this MR do and why?

Most offenses were resolved using auto-correct feature.

MR extracted while working on #356448 (closed).

Screenshots or screen recordings

n/a

How to set up and validate locally

tests=$(tff -f tests.yml $(git diff --name-only origin/master))
bin/rspec $tests 

REVEAL_RUBOCOP_TODO=1 bundle exec rubocop $(git diff --name-only origin/master | grep -v yml)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.