Merged patch series from Avi Kivity:
In rare but valid cases (reconciling many tombstones, paging disabled),
a reconciled_result can grow large. This triggers large allocation
warnings. Switch to chunked_vector to avoid the large allocation.
In passing, fix chunked_vector's begin()/end() const correctness, and
add the reverse iterator function family which is needed by the conversion.
Fixes#4780.
Tests: unit (dev)
Commit Summary
utils: chunked_vector: make begin()/end() const correct
utils::chunked_vector: add rbegin() and related iterators
reconcilable_result: use chunked_vector to hold partitions