Auto merge of #62038 - Zoxc:pre-gc-dep-graph, r=<try>

[WIP] Make dep node indices persistent between sessions

This makes marking dep nodes green faster (and lock free in the case with no diagnostics). This change is split out from #60035.

Unlike #60035 this makes loading the dep graph slower because it loads 2 copies of the dep graph, one immutable and one mutable.

Based on #61845, #61779 and #61923.

Author: bors

Cargo.lock

@@ -2893,6 +2893,7 @@ name = "rustc_data_structures"
 version = "0.0.0"
 dependencies = [
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "crossbeam-utils 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "ena 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "graphviz 0.0.0",
  "indexmap 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",