Auto merge of #59626 - nnethercote:DepGraph-1.02x, r=<try>

Reduce the `DepNode` pre-allocation ratio.

A code size of increase of 15% is overly generous. 2% is more realistic.

This change reduces peak memory size by 20+ MiB on some workloads.

r? @Zoxc

Author: bors

src/librustc/dep_graph/graph.rs

@@ -993,7 +993,7 @@ impl CurrentDepGraph {
         // Pre-allocate the dep node structures. We over-allocate a little so
         // that we hopefully don't have to re-allocate during this compilation
         // session.
-        let new_node_count_estimate = (prev_graph_node_count * 115) / 100;
+        let new_node_count_estimate = (prev_graph_node_count * 102) / 100;
 
         CurrentDepGraph {
             data: IndexVec::with_capacity(new_node_count_estimate),