deps: Upgrade Flutter to 3.32.0-1.0.pre.257

And update Flutter's supporting libraries to match.

In particular this pulls in a recent PR of mine so we can use it:
  flutter/flutter#166730

Author: gnprice

pubspec.lock

@@ -650,26 +650,26 @@ packages:
     dependency: transitive
     description:
       name: leak_tracker
-      sha256: "6bb818ecbdffe216e81182c2f0714a2e62b593f4a4f13098713ff1685dfb6ab0"
+      sha256: "8dcda04c3fc16c14f48a7bb586d4be1f0d1572731b6d81d51772ef47c02081e0"
       url: "https://pub.dev"
     source: hosted
-    version: "10.0.9"
+    version: "11.0.1"
   leak_tracker_flutter_testing:
     dependency: transitive
     description:
       name: leak_tracker_flutter_testing
-      sha256: f8b613e7e6a13ec79cfdc0e97638fddb3ab848452eff057653abd3edba760573
+      sha256: "1dbc140bb5a23c75ea9c4811222756104fbcd1a27173f0c34ca01e16bea473c1"
       url: "https://pub.dev"
     source: hosted
-    version: "3.0.9"
+    version: "3.0.10"
   leak_tracker_testing:
     dependency: transitive
     description:
       name: leak_tracker_testing
-      sha256: "6ba465d5d76e67ddf503e1161d1f4a6bc42306f9d66ca1e8f079a47290fb06d3"
+      sha256: "8d5a2d49f4a66b49744b23b018848400d23e54caf9463f4eb20df3eb8acb2eb1"
       url: "https://pub.dev"
     source: hosted
-    version: "3.0.1"
+    version: "3.0.2"
   legacy_checks:
     dependency: "direct dev"
     description:
@@ -1355,5 +1355,5 @@ packages:
     source: path
     version: "0.0.1"
 sdks:
-  dart: ">=3.8.0-265.0.dev <4.0.0"
-  flutter: ">=3.32.0-1.0.pre.87"
+  dart: ">=3.9.0-55.0.dev <4.0.0"
+  flutter: ">=3.32.0-1.0.pre.257"

pubspec.yaml

@@ -14,8 +14,8 @@ environment:
   # We use a recent version of Flutter from its main channel, and
   # the corresponding recent version of the Dart SDK.
   # Feel free to update these regularly; see README.md for instructions.
-  sdk: '>=3.8.0-265.0.dev <4.0.0'
-  flutter: '>=3.32.0-1.0.pre.87'  # 427f8c8e1569e1d2dba4583ef27cc06baa744108
+  sdk: '>=3.9.0-55.0.dev <4.0.0'
+  flutter: '>=3.32.0-1.0.pre.257'  # b90818ec53ac6f774cdeebd2acd9ab8e71b5c7b5
 
 # To update dependencies, see instructions in README.md.
 dependencies: