Consolidate insert into PruneAccessor

[hildebrandmw]

The insert followup to #1067.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 84.24125% with 81 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.40%. Comparing base (d44b9a8) to head (f03ebbe).

Files with missing lines	Patch %	Lines
diskann/src/provider.rs	16.00%	21 Missing ⚠️
...rs/src/model/graph/provider/async_/inmem/scalar.rs	56.66%	13 Missing ⚠️
...s/src/model/graph/provider/async_/inmem/product.rs	78.00%	11 Missing ⚠️
diskann-bftree/src/provider.rs	87.80%	10 Missing ⚠️
...src/model/graph/provider/async_/inmem/spherical.rs	50.00%	10 Missing ⚠️
diskann-garnet/src/provider.rs	87.69%	8 Missing ⚠️
diskann-providers/src/index/wrapped_async.rs	0.00%	6 Missing ⚠️
diskann/src/graph/index.rs	99.28%	1 Missing ⚠️
diskann/src/graph/test/provider.rs	98.18%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1138      +/-   ##
==========================================
- Coverage   89.45%   89.40%   -0.06%     
==========================================
  Files         484      484              
  Lines       91407    91333      -74     
==========================================
- Hits        81765    81653     -112     
- Misses       9642     9680      +38     

Flag	Coverage Δ
miri	89.40% <84.24%> (-0.06%)	⬇️
unittests	89.05% <84.24%> (-0.06%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
diskann-benchmark-core/src/build/graph/multi.rs	98.92% <100.00%> (ø)
diskann-benchmark-core/src/build/graph/single.rs	100.00% <100.00%> (ø)
...benchmark-core/src/streaming/graph/drop_deleted.rs	98.03% <100.00%> (ø)
diskann-providers/src/index/diskann_async.rs	96.20% <100.00%> (ø)
...roviders/src/model/graph/provider/async_/common.rs	90.05% <ø> (+1.75%)	⬆️
...iders/src/model/graph/provider/async_/distances.rs	60.86% <ø> (+21.43%)	⬆️
...odel/graph/provider/async_/inmem/full_precision.rs	98.52% <100.00%> (-0.02%)	⬇️
.../src/model/graph/provider/async_/inmem/provider.rs	92.51% <100.00%> (ø)
diskann-vector/src/traits.rs	100.00% <100.00%> (ø)
diskann/src/graph/glue.rs	90.72% <ø> (ø)
... and 12 more

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