deps: Upgrade Flutter to latest main, 3.16.0-23.0.pre.38

And update Flutter's supporting libraries to match.

pubspec.lock

@@ -648,18 +648,10 @@ packages:
     dependency: transitive
     description:
       name: leak_tracker
-      sha256: f38a2c91c12f31726ca13015fbab3d2e9440edcb7c17b8b36ed9b85ed6eee6a2
+      sha256: "2c30f27ada446b4d36307aade893faaaeb6d8f55b2362b7f424a9668fcc43f4d"
       url: "https://pub.dev"
     source: hosted
-    version: "9.0.11"
-  leak_tracker_flutter_testing:
-    dependency: transitive
-    description:
-      name: leak_tracker_flutter_testing
-      sha256: "23770c69594f5260a79fe9d84e29f8b175d1b05d128e751c904b3cdf910e5dfc"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.9"
+    version: "9.0.14"
   leak_tracker_testing:
     dependency: transitive
     description:
@@ -1173,10 +1165,10 @@ packages:
     dependency: transitive
     description:
       name: vm_service
-      sha256: a13d5503b4facefc515c8c587ce3cf69577a7b064a9f1220e005449cf1f64aad
+      sha256: b3d56ff4341b8f182b96aceb2fa20e3dcb336b9f867bc0eafc0de10f1048e957
       url: "https://pub.dev"
     source: hosted
-    version: "12.0.0"
+    version: "13.0.0"
   watcher:
     dependency: transitive
     description:
@@ -1258,5 +1250,5 @@ packages:
     source: hosted
     version: "3.1.2"
 sdks:
-  dart: ">=3.3.0-56.0.dev <4.0.0"
-  flutter: ">=3.16.0-17.0.pre.36"
+  dart: ">=3.3.0-91.0.dev <4.0.0"
+  flutter: ">=3.16.0-23.0.pre.38"

pubspec.yaml

@@ -24,8 +24,8 @@ environment:
   # that by the time we want to release, these will have become stable.
   # TODO: Before general release, switch to stable Flutter and Dart versions,
   #   or pin exact versions: https://github.com/zulip/zulip-flutter/issues/15
-  sdk: '>=3.3.0-56.0.dev <4.0.0'
-  flutter: '>=3.16.0-17.0.pre.36'
+  sdk: '>=3.3.0-91.0.dev <4.0.0'
+  flutter: '>=3.16.0-23.0.pre.38'
 
 # Dependencies specify other packages that your package needs in order to work.
 # To automatically upgrade your package dependencies to the latest versions