Upgrade AGP to 8.9.1 (#10458)
Upgrades AGP to 8.9.1. A few dependabot PRs are stuck because they are failing with similar error messages:
```
* What went wrong:
Execution failed for task ':app:checkDebugAarMetadata'.
> A failure occurred while executing com.android.build.gradle.internal.tasks.CheckAarMetadataWorkAction
> An issue was found when checking AAR metadata:
1. Dependency 'androidx.browser:browser:1.9.0' requires Android Gradle plugin 8.9.1 or higher.
This build currently uses Android Gradle plugin 8.6.0.
```
Blocked PRs:
* https://github.com/flutter/packages/pull/9855
* https://github.com/flutter/packages/pull/10045
## Pre-Review Checklist
Roll Flutter from 9f383e099033 to d438df35f998 (18 revisions) (#10491)
https://github.com/flutter/flutter/compare/9f383e099033...d438df35f998
2025-11-21 jason-simmons@users.noreply.github.com [ Tool ] Use a separate output directory when the native hooks run the build system (flutter/flutter#178840)
2025-11-21 dolt@guide.inc Fix Windows Enter key after focus loss (flutter/flutter#178523)
2025-11-21 engine-flutter-autoroll@skia.org Roll Dart SDK from 369795548c09 to c788b6a7aefd (1 revision) (flutter/flutter#178924)
2025-11-21 engine-flutter-autoroll@skia.org Roll Skia from 51fd48dccfb8 to d4e9d2873bfd (4 revisions) (flutter/flutter#178912)
2025-11-21 1063596+reidbaker@users.noreply.github.com Add changelog for 3.38.2 (flutter/flutter#178796)
2025-11-21 engine-flutter-autoroll@skia.org Roll Dart SDK from 003a42bad376 to 369795548c09 (2 revisions) (flutter/flutter#178899)
2025-11-21 engine-flutter-autoroll@skia.org Roll Skia from b9eafe0fab0c to 51fd48dccfb8 (1 revision) (flutter/flutter#178897)
2025-11-21 engine-flutter-autoroll@skia.org Roll Dart SDK from 0894b46fff76 to 003a42bad376 (1 revision) (flutter/flutter#178889)
2025-11-21 ahmedsameha1@gmail.com Make sure that a TextSelectionToolbarTextButton doesn't crash in 0x0 … (flutter/flutter#178374)
2025-11-21 ahmedsameha1@gmail.com Make sure that a CupertinoSpellCheckSuggestionsToolbar doesn't crash … (flutter/flutter#177978)
2025-11-21 ahmedsameha1@gmail.com Make sure that a TabBar doesn't crash in 0x0 environment (flutter/flutter#178201)
2025-11-20 ahmedsameha1@gmail.com Make sure that a ToggleButtons doesn't crash in 0x0 environment (flutter/flutter#178454)
2025-11-20 engine-flutter-autoroll@skia.org Roll Skia from d7b961c5f305 to b9eafe0fab0c (6 revisions) (flutter/flutter#178888)
2025-11-20 97480502+b-luk@users.noreply.github.com Add macrobenchmark perf test for drawing arcs (flutter/flutter#178690)
2025-11-20 engine-flutter-autoroll@skia.org Roll Dart SDK from 5b21f8a7d5d3 to 0894b46fff76 (1 revision) (flutter/flutter#178881)
2025-11-20 engine-flutter-autoroll@skia.org Roll Skia from 6284b4f09e14 to d7b961c5f305 (1 revision) (flutter/flutter#178867)
2025-11-20 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from 0z3qxzY6CWb8iVxEf... to Y-cMdgKy3d6EnibWR... (flutter/flutter#178865)
2025-11-20 engine-flutter-autoroll@skia.org Roll Packages from 8f72e4b9d66e to b1e2fb049013 (6 revisions) (flutter/flutter#178868)
If this roll has caused a breakage, revert this CL and stop the roller
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https://autoroll.skia.org/r/flutter-packages
Please CC louisehsu@google.com,stuartmorgan@google.com on the revert to ensure that a human
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