Adopt rubocop and format the project

[st0012]

In addition to having a consistent coding style through CI checks, anyone uses a LSP server (whether Ruby LSP or Solargraph) will have auto-formatting in their editor as well.

1. After checking different rubocop rules, I think rubocop-rails-omakase's rules match my taste the most but also doesn't require much changes in our codebase.
   • I didn't use standard as it's not supported by Ruby LSP atm
2. I ran rubocop -a on the entire project to apply the styles, with a couple of manual adjustments.
3. I also added a new CI job for linting.

#skip-changelog

[github-actions]

• 🚫 Please pin the action by specifying a commit SHA instead of a tag/branch.

[codecov]

Codecov Report

Merging #2241 (c534ee5) into master (3377a28) will increase coverage by 0.02%.
The diff coverage is 93.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2241      +/-   ##
==========================================
+ Coverage   97.41%   97.43%   +0.02%     
==========================================
  Files         102      102              
  Lines        3823     3823              
==========================================
+ Hits         3724     3725       +1     
+ Misses         99       98       -1     

Components	Coverage Δ
sentry-ruby	98.10% <100.00%> (ø)
sentry-rails	95.05% <50.00%> (ø)
sentry-sidekiq	94.70% <100.00%> (ø)
sentry-resque	93.65% <ø> (+1.58%)	⬆️
sentry-delayed_job	95.60% <ø> (ø)
sentry-opentelemetry	100.00% <100.00%> (ø)

Files	Coverage Δ
...entry-delayed_job/lib/sentry/delayed_job/plugin.rb	100.00% <ø> (ø)
...entelemetry/lib/sentry/opentelemetry/propagator.rb	100.00% <100.00%> (ø)
...lemetry/lib/sentry/opentelemetry/span_processor.rb	100.00% <100.00%> (ø)
sentry-rails/app/jobs/sentry/send_event_job.rb	60.00% <ø> (ø)
sentry-rails/lib/sentry/rails/configuration.rb	97.14% <ø> (ø)
...ls/lib/sentry/rails/tracing/abstract_subscriber.rb	74.07% <ø> (ø)
.../sentry/rails/tracing/active_storage_subscriber.rb	100.00% <ø> (ø)
sentry-ruby/lib/sentry-ruby.rb	96.44% <ø> (ø)
sentry-ruby/lib/sentry/check_in_event.rb	100.00% <100.00%> (ø)
sentry-ruby/lib/sentry/configuration.rb	98.78% <100.00%> (ø)
... and 17 more

... and 1 file with indirect coverage changes

[st0012]

In addition to not liking this style myself, having it enabled requires changing almost all array literals in the codebase (~500 more offences). So I decided to not take this one in.

[st0012]

@sl0thentr0py 👋 let me know if you have concern about this?

[sl0thentr0py]

nice, thx!