For both main and staging (which must both exist and not be oversized), return the combined respective feerate diagrams, including chunks from all clusters, but excluding clusters that appear identically in both. Use FeeFrac rather than FeePerWeight so CompareChunks is usable without type-conversion.
Declared in <txgraph.h>
virtual
std::pair<std::vector<FeeFrac>, std::vector<FeeFrac>>
GetMainStagingDiagrams() noexcept = 0;
A pair holding the main graph's and staging graph's combined feerate diagrams.