feat(pii): Wire `user_info` auto-population gating

[sl0thentr0py]

Stack position: 8/10. Blocked by #3002**.**

Gate auto-populated user identity/IP behind data_collection.user_info.

Scope

• sentry-ruby/lib/sentry/event.rb: user IP / identity auto-population gated by user_info.
• sentry-rails/lib/sentry/rails/active_job.rb:40-44: user propagation to async jobs gated by user_info.
• Critical (per spec): data_collection guards writing data to the scope via instrumentation, not reading it. User-set data (Sentry.set_user, before_send, manual scope) MUST never be gated and must always attach even when user_info = false.
• Coordinate the request-IP gate ownership with feat(pii): Wire core request interface to data_collection #3003 (request interface) to avoid double-gating.

Files & tests

• event.rb, sentry-rails/.../active_job.rb
• spec/active_job/shared_examples/tracing/user_propagation.rb and related event specs
• Add a regression test proving set_user survives user_info = false.

[linear-code]

RUBY-195