[roll] Roll fuchsia [rust] Migrate to rust edition 2021

This migrates the majority of our rust code and build files to use edition 2021. See https://doc.rust-lang.org/edition-guide/rust-2021/index.html for details about the new edition.

The edition migration tooling added lots of code like `let _ = &self;` to preserve the drop ordering of the original code. See https://doc.rust-lang.org/edition-guide/rust-2021/disjoint-capture-in-closures.html for more information about that specific change.

Original-Bug: 101302
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/691339
Original-Revision: 30357e2cfcd4c3b68afcb776508b53f7c0b3d4cd
GitOrigin-RevId: 61bb68411228571703643c1dfb44906f5ef25ed4
Change-Id: Iaa8f2a8aff857027290b9c85446bf989f932f380
diff --git a/stem b/stem
index 272a024..0dc4815 100644
--- a/stem
+++ b/stem
@@ -10,7 +10,7 @@
              githooks=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="6532585e2fbc52292a6fddff3a564982d1b7bf09"/>
+             revision="30357e2cfcd4c3b68afcb776508b53f7c0b3d4cd"/>
   </projects>
   <hooks>
     <hook name="install-environment"