Avoid using platform ProcessInfo.maxRss in test. (#158526)

Closes https://github.com/flutter/flutter/issues/157629.

Avoids failures in the style:
```txt
00:37 +4597 ~3 -1: /Users/matanl/Developer/flutter/packages/flutter_tools/test/commands.shard/permeable/build_appbundle_test.dart: analytics logs success [E]                                                                                                        
  Expected: contains Event:<{"eventName":"flutter_command_result","eventData":{"commandPath":"create","result":"success","commandHasTerminal":false,"maxRss":147013632}}>
    Actual: [
              Event:{"eventName":"command_usage_values","eventData":{"workflow":"create","commandHasTerminal":false,"createProjectType":"app","createAndroidLanguage":"kotlin","createIosLanguage":"swift"}},
              Event:{"eventName":"flutter_command_result","eventData":{"commandPath":"create","result":"success","commandHasTerminal":false,"maxRss":143261696}},
              Event:{"eventName":"timing","eventData":{"workflow":"flutter","variableName":"create","elapsedMilliseconds":527,"label":"success"}},
              Event:{"eventName":"command_usage_values","eventData":{"workflow":"appbundle","commandHasTerminal":false,"buildAppBundleTargetPlatform":"android-arm,android-arm64,android-x64","buildAppBundleBuildMode":"release"}},
              Event:{"eventName":"flutter_command_result","eventData":{"commandPath":"appbundle","result":"success","commandHasTerminal":false,"maxRss":147013632}},
              Event:{"eventName":"timing","eventData":{"workflow":"flutter","variableName":"appbundle","elapsedMilliseconds":10,"label":"success"}}
            ]
     Which: does not contain Event:<{"eventName":"flutter_command_result","eventData":{"commandPath":"create","result":"success","commandHasTerminal":false,"maxRss":147013632}}>
```

I am guessing <https://api.flutter.dev/flutter/dart-io/ProcessInfo/maxRss.html> is not guaranteed to be stable while running, and as a result is not. This stabilizes the value for a test that I believe does not care about getting the "real" value anyway.

packages/flutter_tools/test/commands.shard/permeable/build_appbundle_test.dart

@@ -7,6 +7,7 @@ import 'package:file/memory.dart';
 import 'package:flutter_tools/src/android/android_builder.dart';
 import 'package:flutter_tools/src/android/android_sdk.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/commands/build_appbundle.dart';
@@ -27,6 +28,7 @@ void main() {
   group('analytics', () {
     late Directory tempDir;
     late FakeAnalytics fakeAnalytics;
+    late FakeProcessInfo processInfo;
 
     setUp(() {
       tempDir = globals.fs.systemTempDirectory.createTempSync('flutter_tools_packages_test.');
@@ -34,6 +36,7 @@ void main() {
         fs: MemoryFileSystem.test(),
         fakeFlutterVersion: FakeFlutterVersion(),
       );
+      processInfo = FakeProcessInfo();
     });
 
     tearDown(() {
@@ -135,7 +138,7 @@ void main() {
             commandPath: 'create',
             result: 'success',
             commandHasTerminal: false,
-            maxRss: globals.processInfo.maxRss,
+            maxRss: processInfo.maxRss,
           ),
         ),
       );
@@ -143,6 +146,7 @@ void main() {
     overrides: <Type, Generator>{
       AndroidBuilder: () => FakeAndroidBuilder(),
       Analytics: () => fakeAnalytics,
+      ProcessInfo: () => processInfo,
     });
   });
 
@@ -291,3 +295,8 @@ class FakeAndroidSdk extends Fake implements AndroidSdk {
   @override
   final Directory directory;
 }
+
+class FakeProcessInfo extends Fake implements ProcessInfo {
+  @override
+  int maxRss = 123456789;
+}