[MOD-13853] Add throttle control callback signature for disk tiered index

[meiravgri]

Add throttle callback function pointers to TieredHNSWDiskParams for enabling/disabling Redis command postponing

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Note

Medium Risk
Public API/ABI change to a shared header struct; consumers must be rebuilt/updated and incorrect initialization could lead to null-callback crashes if not handled by callers.

Overview
Adds a new ThrottleCB callback type and extends TieredHNSWDiskParams to include enableThrottleCB/disableThrottleCB hooks for toggling Redis command postponing during disk-tiered index operations.

Replaces the prior placeholder field in TieredHNSWDiskParams, updating the public initialization parameter surface for disk-tiered HNSW.

^{Written by Cursor Bugbot for commit d671e69. This will update automatically on new commits. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.08%. Comparing base (de564b0) to head (d671e69).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #908      +/-   ##
==========================================
- Coverage   97.12%   97.08%   -0.05%     
==========================================
  Files         129      129              
  Lines        7500     7500              
==========================================
- Hits         7284     7281       -3     
- Misses        216      219       +3     

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