feat: Add support for $SENTRY_DEBUG and $SENTRY_SPOTLIGHT

[BYK]

Part of getsentry/spotlight#482. Similar to getsentry/sentry-python#3443 but it also adds support for $SENTRY_DEBUG which was lacking in the Ruby SDK.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.71%. Comparing base (ec70677) to head (5a4f042).
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #2374       +/-   ##
===========================================
+ Coverage   78.10%   98.71%   +20.61%     
===========================================
  Files         149      210       +61     
  Lines        7011    13904     +6893     
===========================================
+ Hits         5476    13726     +8250     
+ Misses       1535      178     -1357     

Components	Coverage Δ
sentry-ruby	99.08% <100.00%> (+43.95%)	⬆️
sentry-rails	97.43% <ø> (ø)
sentry-sidekiq	97.01% <ø> (ø)
sentry-resque	97.11% <ø> (ø)
sentry-delayed_job	98.92% <ø> (ø)
sentry-opentelemetry	100.00% <ø> (ø)

Files	Coverage Δ
sentry-ruby/lib/sentry/configuration.rb	98.82% <100.00%> (+18.59%)	⬆️
sentry-ruby/lib/sentry/utils/env_helper.rb	100.00% <100.00%> (ø)
sentry-ruby/spec/sentry/configuration_spec.rb	100.00% <100.00%> (ø)

... and 126 files with indirect coverage changes

[BYK]

Astonished that it only took me like 5 tries to get it right 🤣

[sl0thentr0py]

I would like a couple of tests in spotlight_transport_spec.rb but if you don't wanna figure out rspec I can also take care of that, lmk