[lazerg]

Why: Redis commands and connects that run outside any active span (blocking XREAD loops, ioredis cluster slot refreshes, background jobs) each start their own trace and get sampled as root transactions with no context. The older ioredis instrumentation already required a parent, so this does the same for the native node-redis:*/ioredis:* channels, the node-redis v4/v5 orchestrion channels, and legacy redis v2/v3.

How to review: The fix is requiresParentSpan: true on each bindTracingChannelToSpan call, plus an early return in the legacy subscriber. The existing tests expected a standalone redis-connect segment, which is now gone. scenario-no-parent.mjs checks that only the command inside the parent span gets a span.

Fixes #25793
Closes #25798

[Lms24]

I made some changes to this PR, where I'd appreciate a review from someone on the team with more DC experience:

• The legacy path used to subscribe to the channel by hand manually called getActiveSpan() to check for a parent. This is yet another pattern of how we check for an active span where we'd have to adjust client reports again. Now it uses bindTracingChannelToSpan, with deferSpanEnd so the span stays open until the command callback fires.
• Added tests for the various (io)redis versions we had so that the behaviour is covered consistently

[nicohrubec]

after some more internal discussion on the approach for this I'll close this down as superseded by #25879