VarAction2: Use reserve and shrink_to_fit for DSG adjusts vector

src/newgrf.cpp

@@ -6014,6 +6014,9 @@ static void NewSpriteGroup(ByteReader *buf)
 				/* Continue reading var adjusts while bit 5 is set. */
 			} while (HasBit(varadjust, 5));
 
+			/* shrink_to_fit will be called later */
+			group->adjusts.reserve(current_adjusts.size());
+
 			for (const DeterministicSpriteGroupAdjust &adjust : current_adjusts) {
 				group->adjusts.push_back(adjust);
 				OptimiseVarAction2Adjust(va2_opt_state, info, group, group->adjusts.back());

src/newgrf_optimiser.cpp

@@ -2745,6 +2745,8 @@ void OptimiseVarAction2DeterministicSpriteGroup(VarAction2OptimiseState &state,
 			OptimiseVarAction2DeterministicSpriteGroupExpensiveVars(group, info.scope_feature);
 		}
 	}
+
+	if (!dse_candidate) group->adjusts.shrink_to_fit();
 }
 
 static std::bitset<256> HandleVarAction2DeadStoreElimination(DeterministicSpriteGroup *group, VarAction2GroupVariableTracking *var_tracking, bool no_changes)
@@ -3141,6 +3143,8 @@ void HandleVarAction2OptimisationPasses()
 		if (group->dsg_flags & DSGF_CHECK_INSERT_JUMP) {
 			OptimiseVarAction2DeterministicSpriteResolveJumps(group);
 		}
+
+		group->adjusts.shrink_to_fit();
 	}
 }