[roll] Roll fuchsia [radar] Migrate radar clients to use services instead of devfs

Migrates radar-proxy and radarutil from devfs to its FIDL service
(fuchsia.hardware.radar.Service).

Also routes the service capability in devices_test_realm and test_realm
to support integration tests.

Test: radar-proxy-test
Original-Original-Bug: 499466477
Original-Original-Bug: 498864014
Original-Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1593665
Original-Original-Revision: a6d49c5a14b11b79dbeb8d58cad6ca8a8934eb0b
GitOrigin-RevId: 3336d09a90bd10f799488310885e6c565f0d9253
Change-Id: I3e0d60f12092c7f03ed16859f200a52d2c8941eb
Reviewed-on: https://fuchsia-review.googlesource.com/c/integration/+/1695714
Cr-Commit-Position: refs/heads/main@{#196238}

stem

diff --git a/stem b/stem
index b918ac5..d078b53 100644
--- a/stem
+++ b/stem
@@ -8,6 +8,6 @@
             manifest="manifests/platform"
             root=""
             remote="https://fuchsia.googlesource.com/fuchsia"
-            revision="2bec2b971ccb498c46bfe58fbbf6d776e91cec78"/>
+            revision="a6d49c5a14b11b79dbeb8d58cad6ca8a8934eb0b"/>
   </imports>
 </manifest>