[roll] Roll fuchsia [superproject] Roll third_party/sdk-integration Reland "[assembly] Improve hermeticity of assembly"

This is a reland of commit 298739e04c13652b6110365965cbae1a9d19d81d

Diff from original commit: make sure $FFX_ISOLATE_DIR exists before
using it with `mkdir -p`. Manually tested in SI.

Original change's description:
> [assembly] Improve hermeticity of assembly
>
> ... and more specifically the `fuchsia_product_image` rule.
>
> There are two improvements:
>
> 1. Set `--isolate-dir` when calling ffx. This makes sure `ffx` doesn't
>    reach out to cache and config dirs in $HOME, which is naturally
>    non-hermetic. Plus, this makes these `ffx` invocations work in
>    environments where $HOME is not available, like nsjail in infra.
>
> 2. Propagate extra files needed for assembly based on images
>    configuration, these are usually key and key metadata.
>
> With this change in-tree assembly is hermetic, i.e.
> `--spawn_strategy=local` is no longer necessary. Though note that
> in-tree assembly still uses legacy images configuration. Plumbing for
> key and metadata will need to be added when switching to new images
> configuration that's added recently.
>
> Original-Bug: 115151
>
> Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/sdk-integration/+/772582

Original-Bug: 115151
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/sdk-integration/+/774104
Original-Revision: 37bd06d345ade974c076878bb748914a3d01b0a3
GitOrigin-RevId: 2e4c7004b64320a21079ca3008559d021a829216
Roller-URL: https://ci.chromium.org/b/8795274192963436001
CQ-Do-Not-Cancel-Tryjobs: true
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/774222
Original-Revision: 8b73a0ae541777addccee29b6b95a33511ef28e4
Change-Id: Iea6503bdb80bf984cdebed6caa53fa91303e82ae
diff --git a/stem b/stem
index 738ca49..c87f05b 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="db3fbba2263a8b437bb61d76329b5610993f38c7"/>
+             revision="8b73a0ae541777addccee29b6b95a33511ef28e4"/>
   </projects>
   <hooks>
     <hook name="install-environment"