message: improving cost function for true virtuals
  Summary:
  The counts in `callee_caller` / `caller_callee` represent the number of unique call-sites, not just caller/callee relationships.
  This change only affects the cost function, and not the correctness / inner workings of inlining.
diff: @@ -200,8 +200,10 @@ MultiMethodInliner::MultiMethodInliner(
  m_x_dex_callees.insert(callee);
  continue;
  }
  - ++callee_caller[callee][caller];
  - if (++caller_callee[caller][callee] == 1) {
  + auto count = caller_insns.second.size();
  + always_assert(count > 0);
  + callee_caller[callee][caller] += count;
  + if ((caller_callee[caller][callee] += count) == count) {
  // We added a new callee that is only valid via m_caller_virtual_callees
  m_caller_virtual_callees[caller].exclusive_callees.insert(callee);
  }
  