[roll] Roll fuchsia [fidlc] Only introduce one name per import

This CL changes fidlc so that an import like `using fuchsia.mem as mem`
only introduces the name `mem` into the scope. Previously, it introduced
both `fuchsia.mem` and `mem`, leading to inconsistent use of the alias.

This change also makes import aliases more powerful, in that they can be
used to avoid naming conflicts. For example, this FIDL will now compile:

    using foo as foolib;  // alias to avoid collision with the struct
    type foo = struct {};

Test: fx test fidl-compiler
Original-Fixed: 48092
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/577002
Original-Revision: 33cfb821d00dabcdc56ff5b4530379118224f6c9
GitOrigin-RevId: 2fd618ca473b27cb9ce1716da6118df1622ae6bc
Change-Id: I75e1218ba2ca6789d4049537d5bfa4c9718b2f7d
diff --git a/stem b/stem
index 6ab3764..a3a69ac 100644
--- a/stem
+++ b/stem
@@ -10,7 +10,7 @@
              githooks=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="caabfa96f6f9d385fc2034f7173633d9e7970cb6"/>
+             revision="33cfb821d00dabcdc56ff5b4530379118224f6c9"/>
   </projects>
   <hooks>
     <hook name="install-environment"