[flutter_tools] Do not crash if buildXcodeProject temporary directory is deleted before cleanup - #195918

…leted before cleanup

During `buildXcodeProject`, `globals.fs.systemTempDirectory.createTempSync('flutter_ios_build_temp_dir.')` creates a temporary directory for the `xcresult` bundle and optional `pipe_to_stdout` FIFO. If `flutter` receives a termination signal (which triggers `LocalFileSystem.dispose()` and deletes the process-wide system temp directory) or external temp cleanup removes the directory while `xcodebuild` is running, `buildXcodeProject` previously crashed with an unhandled `PathNotFoundException` when writing to `scriptOutputPipeFile` or when calling `tempDir.deleteSync(recursive: true)` in the `finally` block (since `ErrorHandlingDirectory.deleteSync` passes `kSystemCodeCannotFindFile` in `ignoreErrorCodes`, causing `ENOENT` to be rethrown).

Guard `scriptOutputPipeFile.writeAsStringSync('all done')` with `scriptOutputPipeFile.existsSync()` and replace `tempDir.deleteSync(recursive: true)` with `ErrorHandlingFileSystem.deleteIfExists(tempDir, recursive: true)`.

Previous output:
```
+35 -1: xcresults simulator Do not crash if temporary build directory is deleted before cleanup. [E]

  Expected: throws <Instance of 'ToolExit'> with `message`: contains 'Encountered error while building for simulator.'
    Actual: <Instance of 'Future<void>'>
     Which: threw FileSystemException:<FileSystemException: No such file or directory, path = '/.tmp_rand0/flutter_ios_build_temp_dirrand0' (OS Error: No such file or directory, errno = 2)>
            stack package:file/src/backends/memory/common.dart 13:5                                                                                                                              checkExists
                  package:file/src/backends/memory/memory_file_system_entity.dart 64:5                                                                                                           MemoryFileSystemEntity.backing
                  package:file/src/backends/memory/memory_file_system_entity.dart 292:17                                                                                                         MemoryFileSystemEntity.internalDeleteSync
                  package:file/src/backends/memory/memory_file_system_entity.dart 140:7                                                                                                          MemoryFileSystemEntity.deleteSync
                  package:flutter_tools/src/ios/mac.dart 637:13                                                                                                                                  buildXcodeProject
+35 -2: Some tests failed.
```

Current output:
```
+37: All tests passed!
```

…emp-dir-delete

…estWithoutContext

Convert the three temporary build directory deletion tests in `build_ios_test.dart` from `testUsingContext` to `testWithoutContext` using `createTestBuildCommand` and `createTestCommandRunner`.

Thread `FeatureFlags` explicitly through `buildXcodeProject`, `processPodsIfNeeded`, `BuildIOSCommand`, `BuildIOSArchiveCommand`, and `BuildFrameworkCommand`, and defer `FlutterCommand.analytics` access in `BuildSwiftPackage` so `BuildCommand` and `BuildIOSCommand` can be constructed and run without ambient `AppContext` lookups.

…featureFlags imports

- Guard `listenToScriptOutputLine()` in `buildXcodeProject` with `if (!scriptOutputPipeFile!.existsSync()) { return; }` so the pipe listener exits cleanly if `tempDir` disappears while `xcodebuild` or `xcode_backend` is running.

- Wrap the terminal-session regression test in `ErrorHandlingFileSystem` and initialize an empty pipe file by default in `_PipeOperatingSystemUtils` so the test exercises `listenToScriptOutputLine()`.

- Restrict `features.dart` imports to `show FeatureFlags` in `build_ios_framework.dart`, `build_ios.dart`, `mac.dart`, and `cocoapod_utils.dart`, and privatize `_BuildIOSSubCommand._featureFlags`.

…p-dir-delete

…letion