Update gradle to 7.5.1 (flutter/engine#45113)

fixes flutter/flutter#133259
Added gradle update instructions and bumped gradle version.

DEPS

@@ -684,7 +684,9 @@ deps = {
   'src/third_party/gradle': {
     'packages': [
       {
-        'version': 'version:7.0.2',
+        # See tools/gradle/README.md for update instructions.
+        # Version here means the CIPD tag.
+        'version': 'version:7.5.1',
         'package': 'flutter/gradle'
       }
     ],

engine/src/flutter/tools/gradle/README.md

@@ -0,0 +1,26 @@
+# Updating gradle version used in engine repo
+
+The instructions in this README explain how to create a CIPD package that
+contains the gradle build-time dependency of the Android embedding of the Engine.
+The Android embedder is shipped to Flutter end-users, but gradle is not.
+
+## Requirements
+
+1. If you have a flutter/engine checkout, then you should already have
+[Depot tools](http://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html#_setting_up) on your path.
+1. Ensure you have write access for cipd. go/flutter-luci-cipd
+1. Download the new version of gradle then verify the checksum,
+and unzip into a local directory.
+
+## Update CIPD Steps
+These steps use gradle version 7.5.1 as an example.
+
+1. Unzip gradle into a folder `unzip gradle-7.5.1-all.zip`
+1. Authenticate with cipd `cipd auth-login`
+1. Run `cipd create -in gradle-7.5.1 -install-mode copy -tag version:7.5.1 -name flutter/gradle`
+1. Update `engine/src/flutter/DEPS` gradle entry to contain the tag from the command above.
+1. Run `gclient sync` to verify that dependency can be fetched.
+
+## Useful links
+* CIPD gradle https://chrome-infra-packages.appspot.com/p/flutter/gradle/+/
+* Gradle Releases https://gradle.org/releases/