[WIP] Remove global delayed-data runtime plumbing

[lquerel]

Not ready for review. #2471 must be merged first to reduce the scope of this PR

Change Summary

Remove the old runtime-managed delayed-data path now that node-local wakeups and node-local delayed resume are in place.

This PR deletes the remaining global delayed-data plumbing from the engine, including the runtime control path and the delayed-data-specific node control message flow. After the previous PRs:

• wakeup-style local scheduling is handled locally in ProcessorInbox
• retry-style delayed pdata resume is handled locally via requeue_later(...)

This is the cleanup step in the redesign tracked in #2465. It simplifies the runtime manager, reduces global contention, and makes shutdown behavior easier to reason about by removing delayed-data-specific special cases from the global control path.

What issue does this PR close?

• Part of Improve control delivery, shutdown robustness, and local deferred work #2465

How are these changes tested?

• Removed or updated engine tests that previously depended on the global
  delayed-data path
• Re-ran the existing coverage for:
  • local wakeups
  • local delayed resume
  • retry behavior
  • shutdown behavior
• Verified with:
  • cargo xtask check

Are there any user-facing changes?

No user-facing changes.

This PR is an internal runtime cleanup only.

[codecov]

Codecov Report

❌ Patch coverage is 77.98834% with 906 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.17%. Comparing base (5ef4ab5) to head (b33cf2b).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2472      +/-   ##
==========================================
- Coverage   88.35%   88.17%   -0.19%     
==========================================
  Files         603      608       +5     
  Lines      212379   215944    +3565     
==========================================
+ Hits       187646   190403    +2757     
- Misses      24207    25015     +808     
  Partials      526      526              

Components	Coverage Δ
otap-dataflow	90.09% <77.98%> (-0.29%)	⬇️
query_abstraction	80.61% <ø> (ø)
query_engine	90.74% <ø> (ø)
syslog_cef_receivers	∅ <ø> (∅)
otel-arrow-go	52.44% <ø> (ø)
quiver	91.94% <98.90%> (+0.03%)	⬆️

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