perf: cppgc inheritance rework (#1300)

A lot of the new lines are docs, see the readme for a synopsis. I've
been successfully using this in my R&D branch for a few weeks now with
no issues. Benchmarks (don't have numbers on hand atm) show a notable
improvement in new object creation and op dispatch when there is
inheritance

Author: nathanwhit

Cargo.lock

@@ -41,6 +41,7 @@ deno_path_util.workspace = true
 deno_unsync.workspace = true
 futures.workspace = true
 indexmap.workspace = true
+inventory = "0.3.21"
 libc.workspace = true
 parking_lot.workspace = true
 percent-encoding.workspace = true