[roll] Roll fuchsia [zxtest] thread_local scoped traces.

(1) By introducing a thread_local storage for scoped-traces,
ASSERT are thread safe again.

(2) Fix scoped traces are tied to the thread where they are created,
such that two threads would not interleave traces.

E.g.
T0 -> push trace "foo bar is A"
T1 -> push trace "foo bar is B"
T0 -> pop trace "foo bar is B"
T1 -> error and "foo bar is A" # Wrong trace.

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1153348
Original-Revision: b290266efd16532ef3d2530824ec737e6c2f3804
GitOrigin-RevId: e2fb12c38a9db47eb29c98b3d3cf9dc01def4493
Change-Id: Ia76ffcf03334e1b14184d306b0e32715fa4cdbf5
diff --git a/stem b/stem
index 1a6bf5c..27e615f 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="d93cacfe18a191357b5372366da718c16c8f0eb7"/>
+             revision="b290266efd16532ef3d2530824ec737e6c2f3804"/>
   </projects>
   <hooks>
     <hook name="install-environment"